Flexible ion-conducting membranes with 3D continuous nanohybrid networks for high-performance solid-state metallic lithium batteries

Polyethylene oxide (PEO)-based electrolytes are considered as one of the most promising solid-state electrolytes for next-generation lithium batteries with high safety and energy density; however, the drawbacks such as insufficient ion conductance, mechanical strength and electrochemical stability hinder their applications in metallic lithium batteries. To enhance their overall properties, flexible and thin composite polymer electrolyte (CPE) membranes with 3D continuous aramid nanofiber (ANF)–Li1.4Al0.4Ti1.6(PO4)3 (LATP) nanoparticle hybrid frameworks are facilely prepared by filling PEO–LiTFSI in the 3D nanohybrid scaffolds via a solution infusion way. The construction of the 3D continuous nanohybrid networks can effectively inhibit the PEO crystallization, facilitate the lithium salt dissociation and meanwhile increase the fast-ion transport in the continuous LATP electrolyte phase, and thus greatly improving the ionic conductivity (∼3 times that of the pristine one). With the integration of the 3D continuity and flexibility of the 3D ANF networks and the thermostability of the LATP phase, the CPE membranes also show a wider electrochemical window (∼5.0 V vs. 4.3 V), higher tensile strength (∼4–10 times that of the pristine one) and thermostability, and better lithium dendrite resistance capability. Furthermore, the CPE-based LiFePO4/Li cells exhibit superior cycling stability (133 mAh/g after 100 cycles at 0.3 C) and rate performance (100 mAh/g at 1 C) than the pristine electrolyte-based cell (79 and 29 mAh/g, respectively). This work offers an important CPE design criteria to achieve comprehensively-upgraded solid-state electrolytes for safe and high-energy metal battery applications.