Direct-Contact Microelectrical Measurement of the Electrical Resistivity of a Solid Electrolyte Interface

Because of its effectiveness in blocking electrons, the solid electrolyte interface (SEI) suppresses decomposition reactions of the electrolyte and contributes to the stability and reversibility of batteries.Despite the critical role of SEI in determining the properties of batteries, the electrical properties of SEI layers have never been measured directly.In this paper, we present the first experimental results of the electrical resistivity of a LiF-rich SEI layer measured using a directcontact microelectrical device mounted in an electron microscope.Measurements show that the SEI layer exhibits high electrical resistivity (2.3 × 10 5 Ω•m), which is comparable with those of typical insulating materials.Furthermore, a combined technique of advanced analyses and firstprinciples calculations show that the SEI layer is mainly composed of amorphous LiF and a minute nanocrystalline Li2CO3 compound.The electronic origin responsible for the high