An Investigation On The Basic Characteristics Of The System Of Magnesium Ion Battery

The basic characteristics of magnesium ion battery were systematically investigated in this thesis, where three kinds of electrolyte system were proposed, that is, the solution of Perchloride acid magnesium(Mg(ClO4)2) in N,N-Dimethyl Formamide(DMF), chlorination magnesium (MgCl2) in N,N-Dimethyl Formamide(DMF), and Ethylenediamine tetraacetic acid disodium magnesium salt(EDTA-Mg) in formamide(FA). The conductivity of the electrolyte solutions, the dissolution and deposition of magnesium ions and the electrochemical performance of the electrodes were systematically studied by the measurement of conductivity, electrolysis, discharge curves and SEM. MgxMnO2 was successfully prepared to use as the anode of the magnesium ion battery in our work.The experiment results showed that the dissolution and deposition of magnesium ions occurred in all the three electrolyte systems, among which the FA/EDTA-Mg system was the most prominent. The dissolution of Mg led to the generation of uniformly-distributed round pits on the surface of magnesium strip. But the deposition products were a little looser.The electrolysis current showed different trends in different electrolyte systems, which suggested the different transfer of Mg2+. The experiment results showed that many factors influenced the conductivity of the electrolyte solutions besides the electrolysis current. The electrolyte solution with the highest conductivity did not show the largest electrolysis current. The space between two electrodes had a complex and irregular influence on the electrolysis current. In the electrolytes of DMF/Mg(ClO4)2, DMF/MgCl2 and FA/EDTA-Mg, the electrolysis current values with different space between two electrodes followed the order of I (0.1mm) > I (0.2mm) > I (0.8mm) > I (1mm) > I (3mm) > I (0.5mm), I (0.1mm) > I (0.2mm) > I (0.5mm) > I (1mm) > I (0.8mm) > I (3mm) and I (3mm) > I (0.2mm) > I (0.1mm) > I (1mm) > I (0.5mm) > I (0.8mm), respectively.Mg‖DMF‖MgxMnO2 cells and Mg‖DMF‖C cells were successfully assembled and their discharge performance was studied at the open-circuit voltage of about 1.5V. The open-circuit voltage of a Mg‖FA/EDTA-Mg‖MgxMnO2 cell was above 2.2V. The cells could keep discharging for 10 hours at the current density of 0.2～0.4mA/cm2, which began to discharge at the voltage of 2.09V and discharged stably at the voltage of 1.9V. There were two discharge plateau at 1.8V and 0.9V at constant current of 0.05～0.06mA/cm2. The discharge time and discharge capacity could reach above 70h and 175mAh/g, respectively, when the cut-off current was 0.8V.