Electrochemical and Optical Studies on Aluminum-Ion Conducting Gel-Polymer Electrolytes

In the last three decades, Li-ion batteries have been developed with high energy and power densities to satisfy the need of electrochemical energy storage for portable electronics as well as automobiles. However, limited natural resources of lithium raw materials compelled researchers to investigate alternative battery chemistries beyond lithium, such as aluminum-ion batteries (AIBs). In this work, a set of novel gel-polymer electrolytes (GPEs) based on poly (ethylene oxide) (PEO) host polymer and aluminum sulphate (Al2(SO4)3) ionic salt have been synthesized and characterized by electrochemical and optical means. The optimized 8PEO-10Al2(SO4)3-40EC-42PC (wt.%) GPE composition showed an ambient temperature ionic conductivity of 0.25 mS cm-1 and the variation of ionic conductivity with inverse temperature showed Arrhenius behavior with almost same activation energies of about 0.14 - 0.15 eV for all the compositions studied in this work. DC polarization test on SS/GPE/SS configuration showed that the highest conducting composition is dominantly an ionic conductor (tion ~ 0.99) with negligible electronic conductivity, which is very much advantageous to avoid short circuits within the cell. Linear sweep voltammetry (LSV) studies showed that the electrochemical stability window of optimized GPE is about 3.7 V (Al/Al3+). FTIR studies confirm the dissociation of ionic salt and the amorphous nature of these GPEs. The optimized GPE developed in this study with exceptional electrochemical stability and high ionic conductivity at ambient temperature has the great potential to be used in AIBs.