Functional La@ZIF-8-enhanced composite quasi-solid electrolyte for high-performance Li-metal batteries

This study synthesizes La@Zeolitic imidazolate frameworks-8 (La@ZIF-8) metal–organic framework (MOF) nanoparticles as a coating material for composite quasi-solid-state electrolyte (CQSE). Theoretical calculations and experimental results revealed that incorporating the high-valent rare earth element La(Ⅲ) effectively enhances the anion-anchoring effect, weakens its binding with Li⁺ ions, and facilitates the dissociation of lithium salts. Simultaneously, the polarization phenomenon is suppressed, promoting stable lithium detachment and embedding in the electrodes. The CQSE comprising La@ZIF-8/SiO₂/PAN is produced by embedding SiO₂ nanoparticles into robust polyacrylonitrile (PAN) fiber membranes, followed by surface coating with La@ZIF-8 MOF. As a result, the La@ZIF-8/SiO₂/PAN CQSE demonstrates an ionic conductivity of 6.76 × 10⁻⁴ S/cm and a Li⁺ transfer number of 0.67 at room temperature (25 °C), with an initial discharge capacity of the La@ZIF-8/SiO₂/PAN battery at 138.61mAh g⁻¹. The capacity retention rate was 94.43 % after 200 cycles, with a capacity decay rate of only 0.02785 % per cycle. Thus, La@ZIF-8/SiO₂/PAN CQSE exhibits excellent electrochemical performance and cycling stability, ensuring the efficient and safe utilization of solid-state lithium-metal batteries.