Preparation and Conductivity Analysis of <scp>LLTO</scp> Nanofiber‐Incorporated <scp>PEO</scp>‐<scp>PVDF</scp>‐<scp>HFP</scp>‐<scp>LiClO₄</scp> Solid Polymer Electrolytes for High‐Voltage Lithium Metal Batteries

ABSTRACT This work focuses on the development of a composite polymer electrolyte (CPE) for all‐solid‐state lithium metal batteries (ASSLMBs), integrating LLTO nanofibers into a PEO (polyethylene oxide)‐PVDF‐HFP (poly(vinylidene fluoride‐cohexafluoropropylene)) matrix with LiClO 4 as the lithium salt. The PEO has high ionic conductivity and flexibility, and the PVDF‐HFP has high mechanical strength and electrochemical stability. Therefore, the resulting composite has improved electrochemical performance and mechanical properties. Incorporating LLTO nanofibers enhances ionic conductivity due to the one‐dimensional ion transport pathways provided by the nanofibers while maintaining mechanical integrity and air stability, overcoming the challenges associated with conventional fillers. The prepared CPE demonstrates exceptional electrochemical stability up to 5.1 V versus Li/Li + , making it suitable for high‐voltage applications over traditional polymer electrolytes. The optimized CPE with 15 wt% LLTO provides the ionic conductivity of 1.1 × 10 −5 S cm −1 at room temperature and reaches 1.46 × 10 −4 S cm −1 at 80°C. The assembled LiNi 1/3 Mn 1/3 Co 1/3 PO 4 ||PEO‐PVDF‐HFP‐LiClO₄‐LLTO||Li based 2032 coin cell worked in between 3 and 4.8 V versus Li/Li + potential window without any electrolyte decomposition from 0.5 to 5 mV/s scan rates. Similarly, the fabricated LiFePO₄||PEO‐PVDF‐HFP (1:2)‐LiClO 4 ‐LLTO (15 wt%)||Li cell provides an initial capacity of 149 mAh g −1 at 0.1 C and 85 mAh g −1 at 0.5 C, exploring its potential for lithium metal batteries. Overall, this work offers a promising pathway for developing advanced solid polymer electrolytes for next‐generation lithium metal batteries, which combine high ionic conductivity, excellent electrochemical performances, and robust mechanical properties.