Ionic liquids for electrochemical applications: Correlation between molecular structure and electrochemical stability window

•The electrochemical stability of ionic liquids comprising ammonium cations and Tf2N anion was determined at −33 °C.•The increase of alkyl long chain length in the cations decreases the stability windows for both cathodic and anodic voltages.•The cathodic windows of ether chains ionic liquids look higher than the ones of alkyl chain compounds.•Ionic liquids having alkyl chains show wider anodic limits than ionic liquids with ether chains.•Ammonium cations having one short chain with a different length than the other two showed the widest electrochemical stability.