Composite Protective Layer Composed of Polymer and Ceramic for Protecting Li Metal in All-Solid-State Li Battery

Abstract

Various anode materials for rechargeable Li batteries, lithium metal is an ideal one for high energy density Li batteries. However, the Li-metal anode has severe safety problems and inferior performance in liquid electrolyte-based cell, due to the growth of Li dendrite and side reactions between Li and electrolytes. Use of solid-state electrolytes can solve the safety issues as well as suppress the Li dendrite growth. Solid polymer electrolytes have high flexibility and good interfacial contacts with electrodes. However, the mechanical strength of polymer is not enough to block Li dendrite growth. In the case of oxide-based inorganic electrolytes, they exhibit high ionic conductivity and good mechanical strength. Nevertheless, these inorganic electrolytes are not suitable for all solid-state battery, because their hard and brittle nature results in poor interfacial contacts with electrodes. In this work, we prepared a protective layer composed of ion-conductive polymer and inorganic materials onto the Li metal. It suppressed the lithium dendrite growth and reduced the interfacial resistance between solid electrolyte and lithium electrode. The electrochemical characterization of the protective layer was performed by DC polarization and electrochemical impedance spectroscopy. The solid-state Li/LiNi0.6Co0.2Mn0.2O2 cells was assembled with protected Li anode and solid electrolyte, and their cycling performance was evaluated.