Preparation And Electrochemical Behavior Of Magnesium-based Composite Anode Materials

Comparing with metallic lithium,magnesium is considered as an ideal anode material with promising development prospects due to its high specific capacity?2205 m Ah/g?,high energy density,high safety,low cost,and environmental friendliness.Magnesium-sulfur batteries use elemental sulfur as the cathode active material and high-purity magnesium or magnesium alloys with high energy density as the anode material.Compared with other chemical power sources,magnesium-sulfur batteries have unique advantages: the average discharge voltage is 1.77 V(vs.Mg²⁺/Mg),and the theoretically specific energy is up to 1722 Wh/kg.However,due to the large polarization of the pure magnesium anode,the discharge voltage platform of the practical magnesium-sulfur battery is only 0.8 V,and the discharge specific capacity is only 800 m Ah/g.In order to improve the discharge platform and specific capacity of magnesium-sulfur batteries,Mg/C,Mg/Li,Mg/Ti composite anode materials have been successfully prepared by cold pressing after ball milling.The physical and electrochemical properties of the composite anodes were characterized and analyzed.Furthermore,the electrochemical performance of the Mg-based composite anodes in different electrolyte systems was analyzed.Conductive agent?Super P and conductive graphite?can improve the electrical conductivity of the anode,so the composite materials prepared by the ball milling method can reduce the polarization of the anode effectively.The composite anode leads to a discharge voltage of 1.1¹.3 V for magnesium-sulfur battery.Magnesium-sulfur batteries with the composite anodes prepared by paste coating deliver a discharge specific capacity of 570 m Ah/g.The use of graphite as an additive for the preparation of magnesium/carbon composite anode material improves the electrochemical performance of the magnesium-sulfur battery,and the battery has a discharge specific capacity of 460 m Ah/g at 0.05 C.Magnesium-lithium composite anode materials with different ratios were prepared by mixing the lithium and magnesium powders.For the composite anode with a lithium content of 10 wt%,the electrochemical performance of the battery was significantly improved.In the 0.35 M?HMDS?₂Mg TEGDME electrolyte system,the initial discharge specific capacity was 1000 m Ah/g at 0.01 C and 900 m Ah/g at a large discharge rate of 0.5 C.The battery still shows a specific discharge capacity of 400 m Ah/g after 5 cycles at 0.01 C.After Ti is incorporated into the magnesium powder,the discharge capacity of the battery reaches 1000 m Ah/g with the cut-off voltage of 0.5 V,and the battery shows a capacity of 600 m Ah/g at the discharge voltage region ranged from 1.1 V to 1.4 V.Mg-Ti electrode has a good compatibility in different electrolyte systems,showing good electrochemical performance in 0.5 M MgClO₄/ACN electrolyte.Electrochemical performance was significantly improved at a high discharge rate.The magnesium-sulfur battery with Mg-Ti anode shows the best electrochemical performance at 0.03 C with a specific discharge capacity of 1550 m Ah/g.