Synthesis and electrochemical properties of a perfluorinated ionomer with lithium sulfonyl dicyanomethide functional groups

Abstract

A novel type of perfluorinated ionomer with lithium sulfonyl dicyanomethide functional groups was prepared for Li-ion batteries with high rate performance. The immobile sulfonyl dicyanomethide anion on the backbone of the polymer chain results in the unity transference number of Li⁺ and high ionic conductivity of the ionomer electrolyte, which could prevent problems caused by a concentration gradient in the electrolyte. ¹⁹F NMR and FT-IR confirmed that the polymer was synthesized successfully. With the appropriate solvent, the ionomer electrolyte's ionic conductivities were observed to be as high as 10⁻⁴ S cm⁻¹ at room temperature. The ionomer electrolyte was electrochemically stable up to 4.5 V, and it still had a stable interface with the Li electrode after a long storage time. The ionomer electrolyte has a promising future in practical application for lithium-ion batteries.