Extreme electron-blocking interface for garnet-based solid-state lithium-metal batteries with superior long lifespan

Abstract Garnet oxide is one of the most promising solid-state electrolytes for solid-state lithium metal batteries. However, the traditional interface modification layers cannot completely block electron migrating from the current collector to the interior of the solid-state electrolyte, which promotes the penetration of lithium dendrites. In this work, a highly electron-blocking interlayer composed of potassium fluorine (KF) is developed to inhibit lithium dendrite growth in garnet oxide Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO). Thanks to the interlayer of stable KF with large band gap, the electronic conductivity of LLZTO reduces by two orders of magnitude. The Li symmetric cells using KF interlayer show an ultralong cycle life ~3000 hours at 0.2 mA cm -2 and over 350 hours at 0.5 mA cm -2 respectively. Moreover, an ionic liquid of LiTFSI in C 4 mim-TFSI is screened to wet the cathode interfaces. The solvent-free Li|LLZTO|LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells present a high specific capacity, and a long lifespan of 3500 cycles at 2C with an average coulombic efficiency of 99.99%. This work provides a simple and integrated strategy on high-performance solid-state lithium metal batteries.