The Research On Several Critical Issues Of Magnesium Battery In Organic Solutions

Magnesium is one of the most abundant elements in the world, Magnesiumreserves of China are the most in the world and account for22.5percent of totalmagnesium reserves in the earth’s crust. There are a lot of advantages fordevelopment of magnesium resources in China. Magnesium and lithium are diagonalin the periodic table of the elements. Both ionic radius and chemical properties ofmagnesium are the same as that of lithium. magnesium as electrode has theadvantages of high Faradic capacity, environmental acceptability, reliability, highsafety, and low cost, so the rechargeable magnesium battery is considered as an idealsubstitution for the Li-ion battery in the future.First, a novel type of porous magnesium electrodes with a stable3D copperfoam as current collector for the organic Mg/Air battery were prepared byamperostatic and pulsed electrodeposition of magnesium on copper foam substrates inan electrolyte of1mol L^-1EtMgBr/THF solution, respectively. Optimal parameters ofpulsed electrodeposition were obtained by using the bending cathode at right anglesmeasurement. The surface morphology of the porous electrode was investigated bySEM, and the discharge performance of the porous magnesium electrode was detectedby means of chronoamperometric measurement. The electrochemical stability of3Dcopper foam current collector was examined by cyclic voltammetry, SEM andICP-OES analyses. These experimental results show that the rate capability of theporous magnesium electrode is better than that of the planar magnesium electrode andthe rate capability of the porous magnesium electrode prepared by pulsedelectrodeposition is superior to that of the porous magnesium electrode prepared byamperostatic electrodeposition. The3D structure of copper foam current collectorcould keep excellent stability during the discharging process of the porous magnesiumelectrode.Second, the electrochemical behavior of the aluminum current collector with afresh surface in three kinds of Grignard reagent/THF electrolyte has been studied bycyclic voltammetry in this article. The experimental results show that pitting corrosionpotentials of the scratched aluminum foils in three kinds of Grignard reagent/THFelectrolytic solutions increase in an order of EtMgCl/THF＜EtMgBr/THF＜PhMgCl/THF. Corrosion behaviors of three kinds of aluminum current collectors bydifferent surface treatments processes, which include removal of the oxide film, placing in room temperature，and high temperature oxidation（the heated aluminumfoils）, in1mol·L^-1EtMgBr/THF solution have been investigated by cyclicvoltammetry, EIS, SEM, FT-IR methods. The corrosion resistances of aluminumcurrent collectors by different treatment processes in1mol·L^-1EtMgBr/THF solutionare different in an order of the scratched aluminum foils<the normal aluminum foils<the heating aluminum foils. A thin dense oxide film on aluminum current collectorsincreases the corrosion resistance of aluminum current collector, however, thecorrosion resistance of aluminum current collector with a thick oxide film would bedecreased. The deposition-dissolution behavior of the aluminum current collector witha fresh surface as the cathodes were investigated in1mol·L^-1EtMgBr/THF solution.Magnesium could deposit-dissolve reversibly and no magnesium-aluminum alloy wasfound on the surface of aluminum current collector.Last, two kinds of MoS₂were prepared by the ultrasonic method （S-MoS₂） andthe hydrothermal method （G-MoS₂）. These two MoS₂samples and the commercialMoS₂（N-MoS₂） sample were characterized by SEM, EDS and XRD analyticalmethods. The electrochemical performances of these three kinds of MoS₂, whichassembled into the battery as the cathodes, were investigated by charging-dischargingtests. The charging-discharging tests had shown that the specific discharge capacity ofthe G-MoS₂was160mAh g^-1, the specific discharge capacity of the S-MoS₂was60mAh g^-1, and the specific discharge capacity of the N-MoS₂was30mAh g^-1. theseresults of charging-discharging had shown that the specific discharge capacity of theMoS₂cathode with a loose lamellar structure was higher than that of the MoS₂cathodewith a compact lamellar structure.