Modification of Electrolyte/Cathode Interfaces by Solid-State Electrolyte Thin Films

Abstract

In this study, the bilayers of the lithium phosphorus oxynitride (LiPON) film on LiCoO2 cathode have been deposited using radio frequency (RF) magnetron sputtering with in-situ substrate bias, followed by post-anneal. For the purpose of decreasing charge transfer resistances, the solid-state interfaces between the LiPON solid-state electrolyte and the LiCoO2 cathode have been modified. By controlling different in-situ substrate bias voltages and anneal times, the properties of both LiPON electrolyte thin films and LiPON/LiCoO2 interface have been altered, as characterized by scanning electron microscopy, X-ray diffraction, impedance spectroscopy, and electron spectroscopy for chemical analysis. It is found that the electrolyte/cathode interfaces are modified in terms of contact structures and interface resistances. After anneal of 30 min. at 200 oC in nitrogen environment, the seams and voids at the interface are eliminated. The charge transfer resistance at the interface has been greatly reduced. As a result, one order of reduction in both interfacial resistance and total cell resistance has been achieved.