Research On Anodematerials Of Rechargeablemagnesium Batteries

Magnesium has similar properties with lithium in many respects, such as ionic radius and chemical properties. Rechargeable magnesium battery is a new kind of green battery which is promising for the application in electric vehicles. In addition, magnesium is relatively inexpensive, environmentally friendly, safe to handle and abundant in resources, so it is absorbing more and more attention from people. At present, research on rechargeable magnesium battery is under elementary development, and focused on cathode materials and electrolyte systems. However, there are few researches about anode materials, and usually use pure Mg as anode materials.To control the dendrite growth and improve the long-term cyclic performance, magnesium alloys were employed as anode materials. The electrochemical properties and surface morphology of AZ31 alloy and commercial pure Mg as anode materials in Mg (AlCl2EtBu)2/THF electrolyte were studied using cyclic voltammetric, constant current charge/discharge and scanning electron microscopy.The results showed that, as anode material of rechargeable magnesium battery, the over-potential of magnesium dissolution-deposition on AZ31 alloy was a little higher than that on commercial pure Mg, and the coulombic efficiency during the initial cycles was lower than that of pure Mg, but the coulombic efficiency of AZ31 remained stable in the long-term cycling compared to pure magnesium. Furthermore, AZ31 alloy effectively restrained the growth of dendrite on the surface of anode material and improved the cyclic performance of batteries.Comparing the cyclic performance and surface morphology of AZ31, AZ61 and AZ91, we found that over-potential of magnesium dissolution-deposition on the alloy electrode increased with the content increase of Al in the alloy. Besides, the stability of long-term cyclic performance and coulombic efficiency decreased and surface roughness of alloy electrode increased. In conclusion, the electrochemical performance of AZ 31 was better than that of AZ61 and AZ91 alloys.Mg-Nd alloys with 1wt%, 2wt% and 3wt% Nd additons were also studied as anode materials of rechargeable magnesium batteries. Magnesium can be reversibly deposited and dissolved on the surface of Mg-Nd alloys and the deposition layer was dense and smooth. Comparing three compositions of Mg-Nd alloys, it found that all three alloy electrodes performed good dissolution-deposition cycling, although unstable fluctuation appeared in the initial several cycles. The process with considerably low over-potential could be obtained after several cycles and the stable cycles were maintained. In addition, the content increase of Nd in the alloy resulted in high over-potential, which leaded to the higher polarization.