Plasticized solid polymer electrolyte based on triblock copolymer poly(vinylidene chloride-co-acrylonitrile-co-methyl methacrylate) for magnesium ion batteries

Abstract

Limited global resources of lithium lead to the consideration of magnesium ion batteries as potential energy storage devices. Magnesium ion batteries have potential for high energy density but require new types of electrode and electrolytes for practical applications. Solid polymer electrolytes offer the opportunity for increased safety and broader electrochemical stability relative to traditional electrolytes. Herein, we report the development of solid polymer electrolyte for magnesium ion batteries based on triblock copolymer poly(vinylidene chloride-co-acrylonitrile-co-methyl methacrylate) (poly(VdCl-co-AN-co-MMA)). The polymer electrolytes are prepared by solution-casting technique using poly(VdCl-co-AN-co-MMA) with various concentrations (10 wt%, 20 wt%, 30 wt%, and 40 wt%) of magnesium chloride (MgCl2) salt. Among the prepared polymer electrolytes, the highest magnesium-ion-conducting polymer electrolyte is 70 wt% poly(VdCl-co-AN-co-MMA):30 wt% MgCl2 polymer–salt composition by electrochemical impedance measurements, and the obtained value of ionic conductivity is found to be in the order of 10−5 S cm−1. Addition of plasticizer succinonitrile in various concentrations (0.1 wt%, 0.2 wt%, 0.3 wt% and 0.4 wt%) with the identified polymer electrolyte of highest conductivity shows increased values of conductivity up to the order of 10−3 S cm−1. Observable changes in crystalline/amorphous nature of the polymer are analyzed using X-ray diffraction pattern. Glass transition temperature of polymer electrolytes has been found using differential scanning calorimetric studies. Transference number measurements have been made to confirm the ionic conductivity. The electrochemical stability for highest conducting plasticized polymer electrolyte is obtained from linear sweep voltammetry as 3.3 V. A primary magnesium ion battery has been constructed with prepared electrolyte of highest conductivity, and its performance and discharge characteristics are also analyzed. The open-circuit voltage of 2.18 V is obtained with the constructed primary magnesium ion battery.