Improving Li dendrite suppression capability of garnet solid-state electrolytes by in situ LiF grain boundary modification

Abstract

Garnet solid-state lithium metal batteries (SSLMBs) have garnered increasing attention as the next-generation energy storage devices. However, the inferior capability of suppressing Li dendrite propagation hinders its further development and application. Herein, an in situ wet synthesis method to homogeneously distribute LiF at the grain boundaries of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is developed to enhance its Li dendrite suppression capability. The introduction of LiF with low electronic conductivity and melting point endows the LLZTO-LiF SSE with extremely low electronic conductivity (1.33 × 10⁻⁹ S cm⁻¹), high relative density (98.8%) and ultralow area specific resistance (5.2 Ω cm²), synergistically suppressing the nucleation and propagation of Li dendrites. As a result, the Li|LLZTO-LiF|Li symmetric cell demonstrates stable performance over 8500 h of cycling at 0.1 mA cm⁻² without experiencing a short circuit. The Li|LLZTO-LiF|LFP full cell exhibits an initial discharge specific capacity of 169.5 mA h g⁻¹ and a superior capacity retention of 89.1% after 200 cycles at 0.1C. This work provides a novel strategy for developing high-performance dendrite-free garnet SSLMBs.