Ultra-thin, scalable, and MOF network-reinforced composite solid electrolyte for all-solid-state lithium metal batteries

Abstract

Ultra-thin, scalable solid-state electrolytes with high mechanical strength are essential for achieving high-performance all-solid-state lithium metal batteries (ASSLMBs). Among various types of solid-state electrolytes, composite solid electrolytes (CSEs) have emerged as an appealing option due to their ability to overcome the limitations of single-component solid-state electrolytes. In this study, ZIF-67 metal-organic framework (MOF) nanoparticles were self-assembled in situ on polyimide (PI) film fibers (referred to as PI@ZIF-67) to create continuous Li⁺ transport channels. The ultra-thin, robust PI fiber film combined with MOF particles imparts high mechanical strength and excellent flexibility to the CSE. Additionally, the abundant sub-nanopores and surface Lewis acidic sites in ZIF-67 nanoparticles facilitate the dissociation of lithium salts and enhance the rapid transport of Li⁺. Consequently, 95 % of the discharge capacity retention of the all-solid-state Li/PI₆₀@ZIF-67-PEO/LFP cell was maintained after 300 cycles at 0.2C and 60 °C. Furthermore, an ultra-long lifespan of 3500 h at 0.2 mA cm⁻² and 0.2 mAh cm⁻² was achieved for the symmetric Li/PI₆₀@ZIF-67-PEO/Li cell. The superior electrochemical performances are attributed to the effective Li⁺ transport network and the high mechanical properties established by the continuous ZIF-67 particles within the PI₆₀@ZIF-67-PEO CSE. This work presents a promising method for the integrated design of ultrathin CSEs that exhibit high ionic conductivity and exceptional mechanical robustness, making them suitable for ASSLMBs.