Evaluation of the Solid-Electrolyte Interphase Formed in the Carbonate-Based Electrolytes with Different Lithium Salts Using the Redox Probe Method

The formation of solid-electrolyte interphase (SEI) on a Pt electrode was investigated in ethylene carbonate (EC) and diethyl carbonate (DEC) containing LiPF6 and lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) using the redox probe method. The formation and properties of the SEI were examined in the electrolytes containing ferrocene as a redox probe. Inhomogeneous and rigid SEI was found to form in 1 M (= mol dm−3) LiPF6/EC+DEC, probably due to the conversion of decomposition products to LiF by the reaction with HF derived from LiPF6. On the other hand, the formation of homogeneous and soluble (or dispersible) SEI was suggested in 1 M LiTFSA/EC+DEC.