Importance of Interlayers on Li Solid-State Batteries Using Ceramic Electrolytes

Abstract

Recently, all solid-state Li ion batteries have received great attention due to its better safety feature. Among several types of inorganic solid electrolyte, Garnet-structured Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is found to exhibit high ionic conductivity with adequate stability especially directly connecting to pure lithium foil as anode. However, it is difficult for inorganic solid electrolyte to have full contact with lithium anode, the high interface polarization and poor wetting ability between solid electrolyte and anode has been a major concern in all state Li ion batteries. Therefore, interface engineering between solid electrolyte and electrodes has been shown to exhibit low interface polarization. In this study, the objective is to investigate the effects of metallic interlayer on reduction of the surface polarization between LLZTO and Li using thin film gold (Au) interlayer. The surface impedance has reduced to less 200ohm/cm2which was demonstrated by EIS measurement and Li stripping/plating tests using a symmetrical cell. The battery behavior was observed by LiCoO2/Ta-LLZO/Li battery, which discharge capacity > 125mAh/g for the first cycle.