Dual-MOFs-cage constructed multistage-channel PVDF-HFP quasi-solid electrolytes for lithium metal battery

Abstract

As the candidate for electrolyte in lithium metal batteries, quasi-solid electrolytes have been affected by the growth of lithium dendrites and the continuous reaction between lithium and electrolyte. Herein, we introduce a quasi-solid electrolyte, ZIF-67@ZIF-8/PVDF-HFP (PHMx), with multi-stage ion transport channels. Additionally, we have developed Zeolitic Imidazolate Frameworks (ZIFs) materials that possess a “cage” structure, which is defined as dual-MC nanoparticles. PVDF-HFP in PHMx serves as mechanical backbone, with dual-MC nanoparticles densely and uniformly distributed within the PVDF-HFP. The synergistic effect of the microporous structure of the PVDF-HFP and that of the dual-MC nanoparticles is utilized to construct multi-stage ion transport channels. PHM9 achieves uniform Li⁺ deposition and inhibits the continuous reaction between lithium and electrolyte. Therefore, PHM9, not only achieves high ionic conductivity of 3.2 × 10⁻³ S cm⁻¹ but also remains stable for 1600 h during Lithium-symmetric cycling. Lithium metal battery, assembled with LiFePO₄ as the cathode material, exhibited stable cycling for 400 cycles at a rate of 0.2 C, demonstrating a capacity retention rate of 86.6 %. Similarly, the lithium metal battery utilizing LiCoO₂ as the cathode material demonstrated stable cycling for 200 cycles at a rate of 0.2 C, exhibiting an impressive capacity retention rate of 96.7 %.