Garnet oxide is one of the most promising solid 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 fluoride (KF) is deposited on garnet oxide Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO). After reacting with melted lithium metal, KF in-situ transforms to KF/LiF interlayer, which can block the electron leakage and inhibit lithium dendrite growth. The Li symmetric cells using the interlayer show a long cycle life of ~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 C₄mim-TFSI is screened to wet the LLZTO|LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) positive electrode interfaces. The Li|KF-LLZTO | NCM cells present a specific capacity of 109.3 mAh g⁻¹, long lifespan of 3500 cycles and capacity retention of 72.5% at 25 °C and 2 C (380 mA g⁻¹) with an average coulombic efficiency of 99.99%. This work provides a simple and integrated strategy on high-performance quasi-solid-state lithium metal batteries.

Textured ceramics with anisotropic ionic conductivity are poised to establish superior ion transport pathways in solid-state electrochemical devices. However, their preparation methods remain a challenge. Here, we develop a gas-solid reactive sintering technique that successfully fabricates a variety of textured lithium ceramics, including electrolyte and electrode materials. These textured lithium ceramic electrolytes exhibit large columnar grains perpendicular to the surface. The textured electrodes indicate an out-of-plane crystallographic texture. As a result, the Li-ion transport pathways across the grain boundary plane are avoided in the textured lithium ceramic with low tortuosity, resulting in great ionic conductivity enhancement by 42 times compared to its traditional equiaxed counterpart. In addition, both Monte Carlo simulation and finite element analysis support the experimental results. This innovative gas-solid reactive sintering technique can extend to prepare various structured and functional ceramics with tailored structures and properties.