Constructing uniform and stable mixed conductive layer to stabilize the solid-state electrolyte/Li interface by cold bonding at mild conditions.

Due to high ionic conductivity, garnet-type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZ) electrolyte has been a promising candidate for high-performance solid-state batteries, while its applications are hindered by interfacial problems. Although the utilization of functional coatings and molten lithium (Li) effectively solves the LLZ interfacial compatibility problem with Li metal, it poses problems such as high cost, high danger, and structural damage. Herein, a mixed conductive layer (MCL) composed of Li 3 N and Li-In alloys was introduced at the LLZ/Li interface (RT-MCL) via an in-situ cold bonding process at room temperature. Such a stable and compact RT-MCL can effectively suppress side reactions and protect the crystal structure of LLZ, and it also promotes uniform Li deposition and inhibits the growth of Li dendrites. The critical current density (CCD) of the Li symmetric cell composed of room temperature formed MCL-LLZ (RT-MCL-LLZ) is increased to 1.8 mA cm -2 and provided stable cycling performance over 2000 hours under 0.5 mA cm -2 . Additionally, this in-situ cold bonding treatment can significantly reduce the cost and eliminate the potential safety issues caused by the high-temperature processing of Li metal. This work highlights the tremendous potential of this in-situ cold bonding technique in the reasonable design and optimization of the LLZ/Li interface. This article is protected by copyright. All rights reserved.