Alginate-based copolymers as the solid-state electrolyte for Mg battery

Abstract

The high theoretical volumetric capacity, abundance of magnesium in the earth’s crust, and the relatively good safety features of Mg metal, have drawn great attention to developing Magnesium batteries as a follow-up to the success of Li-ion battery technology. However, the magnesium metal is incompatible with most electrolyte solvents and salts, which passivates the surface of magnesium and causes the battery failure. One of the crucial approaches to address this problem is to seek novel electrolytes which have good metallic Mg compatibility and subsequently improve the cycling performance.

In this research, the feasibility of combing PEO, Mg-alginate and MgCl2 to design a solid polymer electrolyte (SPE) for Mg-ion batteries has been assessed. The SPE membrane shows a conductivity of ~10-5 S·cm-1 at 60 °C and an increased value up to ~10-4 S·cm-1 at 80 °C and above. The XRD results have suggested there is no real interaction in between the two polymers which can cause reconstruction of the polymer structure. Moreover, this electrolyte material is highlighted with an excellent cycling stability of up to 150 hours. At last, a possible model which could explain the Arrhenius behavior of temperature-dependent ion conduction is proposed for this SPE material. Overall, this research demonstrates the potential application of Mg-alginate for Mg energy storage in terms of developing a polymer electrolyte, despite further modification in the future is needed.