Hierarchical bulk-interface design of MOFs framework for polymer electrolyte towards ultra-stable quasi-solid-state Li metal batteries

The sluggish ion transportation, oxidation instability and severe lithium dendrites impede the development of solid-state lithium metal battery (SSLMBs). Herein, a novel structural design of in-situ polymerized composite electrolyte (CPE) with the utilization of both orientationally arranged and unilaterally sedimented Zeolitic imidazolate framework-67 (ZIF-67) fillers are reported. The in-situ growing of ZIF-67 crystals on 3D polyvinylidene fluoride (PVDF) nanofiber skeleton not only provides high-speed Li⁺ conduction pathway, but also promotes the antioxidative ability of surrounding polymer matrix by facilitating the ring-open polymerization of 1,3-Dioxolane (DOL) monomer to form long-chain PDOL. Meanwhile, ZIF-67 deposition layer constructed through the natural sedimentation of residual ZIF-67 during PVDF@ZIF-67 framework fabrication regulates surface Li⁺ flux towards lithium anode and further optimizes SEI composition. As a result, satisfactory ionic conductivity of 1.8 × 10⁻⁴ S cm⁻¹ and oxidative potential of 5.9 V (vs. Li⁺/Li) are acquired for unilateral-sedimented ZIF-67/PDOL CPE (UZE). Encouragingly, symmetric Li battery based on UZE displays a superior stability over 2300 h at 0.1 mA cm⁻² and a remarkable cycle durability with 92.5 % of capacity retained after 570 cycles at 2C is also achieved for Li||LFP battery. This study provides a novel guidance in engineering solid electrolyte with excellent ionic transport kinetics and interfacial compatibility for next-generation SSLMBs.