Investigating Ca-Ion Conduction in PVDF-Based Electrolytes

Beyond Li–ion energy storage is gaining considerable attention owing to several challenges encountered with Lithium metal, such as scarcity, availability, high cost, and safety. Among the best potential alternatives is Calcium, which possesses many properties desirable to Lithium, and is more Earth–abundant, sustainable, and cost–effective [1]. Recent research in battery electrolytes has been directed toward alternatives for liquid electrolytes due to their risk of flammability and leakage. Solid polymer electrolytes (SPEs), gel polymer electrolytes (GPEs), and poly-ionic liquids are a few examples. However, many of these alternatives still lack the ionic conductivity necessary for commercial use. The objective of this work is to develop Ca-ion conducting PVDF-based gel polymer electrolytes (GPEs), wherein N–methylpyrrolidone (NMP) is used as a liquid solvent and Ca(TFSI)₂ as the salt. Specifically, we investigate ionic conductivity in these GPEs as a function of drying temperature and find that at a fixed salt concentration of 0.5 M, ionic conductivity decreases with increase in drying temperature due to decrease in NMP content. The highest ionic conductivity obtained in this study is in the range of 10^-4 S/cm at room temperature and up to 10^-3 S/cm at elevated temperatures [2]. These results are promising, and some areas that could be further explored are its transference number, mechanical strength, and the relationship between salt concentration and ionic conductivity.

[1] Hosein, I. D., ACS Energy Letters. (2021)

[2] Edward C. Fluker, Shreyas Pathreeker, and Ian D. Hosein, The Journal of Physical Chemistry C. (2023)