Magnesium ion-conducting gel polymer electrolytes based on poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN): a comparative study between magnesium trifluoromethanesulfonate (MgTf2) and magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2)

Abstract

In this paper, we report the effects of two different type of salts which are magnesium trifluoromethanesulfonate (MgTf2) and magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2) on ionic conductivity studies, transference number measurements, and electrochemical properties of gel polymer electrolyte (GPE) systems. Both systems used poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN) as the host polymer with the incorporation of plastic crystal succinonitrile (SN) and plasticizer ethylene carbonate (EC) in the ratio of (1:1). The system containing Mg(TFSI)2 exhibits higher in ionic conductivity of ~ (10−7–10−6) S cm−1 compared to the system containing MgTf2 of ~ (10−8–10−7) S cm−1. The conductivity temperature dependence studies of both GPE systems seem to obey the VTF relation. The ionic transference numbers were found to be > 0.9 for all GPEs while the highest cationic transference numbers obtained were 0.56 and 0.59 for MgTf2 system and Mg(TFSI)2 system, respectively. In linear sweep voltammetry (LSV) studies, wider electrochemical stability window was observed for the GPE containing Mg(TFSI)2 than that containing MgTf2 while cyclic voltammetry (CV) confirmed the conduction of Mg2+ ions in the GPEs. The structural and complex formations of the GPEs were confirmed by X-ray diffraction (XRD) analysis and both systems are shown to be amorphous in nature. The Mg/GPE/MgMn2O4 cells were assembled by using the most optimum GPE film from both systems and their charge-discharge performance was studied.