A Microporous Gel Polymer Electrolyte with High Mg2+ Ionic Conductivity at Room Temperature

Rechargeable magnesium batteries have attracted much attention due to the high theoretical volumetric capacity, abundance, and safety. However, solid-state Mg batteries have been rarely studied because of limited choices of solid-state electrolyte materials. In this research, poly(vinylidene fluoride)/poly(propylene carbonate) (PVDF/PPC) as matrix were prepared using a simple solution casting method. Ethylene carbonate (EC), diethyl carbonate (DEC), and magnesium(II) bis(trifluoromethanesulfonyl) imide [Mg(TFSI)₂] were selected to prepare liquid electrolyte. A classification of novel gel polymer electrolytes (GPEs), PVDF/PPC/Mg(TFSI)₂, was synthesized and investigated. The electrochemical measurements show that PVDF/PPC/Mg(TFSI)₂ polymer electrolytes exhibit a high ionic conductivity, close to 10⁻² S cm⁻¹, at room temperature. The electrochemical stability window of PVDF/PPC-based GPE was up to 3 V (versus Mg²⁺/Mg). Materials characterization shows that these GPEs have a porous structure, providing a pathway for magnesium ion transport. Thermal analysis and crystal structure results indicate that PVDF crystallinity was affected by the addition of PPC. Additionally, the ion transport mechanism in the gel polymer electrolyte has been discussed.