Lithium Metal Protected by Composite Electrolyte for All-Solid-State Batteries

Abstract

Lithium ion batteries are used widely because of their high energy density and long cycle life. However, the demand for energy density of batteries is increasing these days. Although lithium metal batteries have been considered one of the attractive candidates for next generation secondary batteries due to high energy density, it is urgent to resolve safety issues about lithium metal as an anode. The protective layer has been proposed as a key for solving these problems by suppressing dendrite and side reaction. In this study, a hybrid protective layer based on poly(ε-caprolactone), nanosized aluminum oxide particles and lithium bis(trifluoromethane-sulfonyl)imide was formed on the lithium metal with solution casting method. The composite layer exhibited an ionic conductivity of 3.2 x 10-5 S/cm at 55 ℃ as well as good electrochemical stability. It alleviated the interfacial resistance between electrode and electrolyte. Lithium metal electrode employing the protective layer was applied to Li/LiNi0.6Co0.2Mn0.2O2 cell, using PCL-based solid electrolyte in electrospun PAI. The cycles of the cell with a composite protective layer exhibited better cycling stability as compared to the cell without layer.