In Situ Deposition and Ultrahigh Vacuum STM/AFM Study of V₂O₅/Li₃PO₄ Interface in a Rechargeable Lithium-Ion Battery

A thin-film solid-state battery was prepared with a vanadium pentoxide cathode and a lithium phosphate electrolyte and studied in situ by ultrahigh vacuum scanning tunneling microscope/atomic force microscopy (STM/AFM). Orientation of the (001) plane of V₂O₅ parallel to the substrate was detected via observation of the periodicity of 11.7 ± 0.5 Å, which is consistent with the unit cell spacing in the 〈100〉 direction. Conductance of the battery was studied locally with the probe tip of the STM/AFM in the regime of mechanical contact with a constant repulsive force. Lateral variation of contact conductance from 0.4 to 2.2 nA was detected as a function of position of the tip in contact with the cathode. The device revealed an extremely high current density of 1 A/cm² due to the low thickness of the electrolyte and the cathode and the concentration of electric field under the scanning probe microscope tip. Transformation of cathode structure due to Li ion intercalation was observed in real time.