Ferroelectric 3D Nanoweb-Incorporated <i>In Situ</i> Cross-Linked Composite Solid Electrolyte for High-Performance Lithium–Metal Polymer Batteries

All-solid-state Li-metal batteries (ASSLBs) are promising for next-generation energy storage systems owing to their high energy density and intrinsic safety. However, their practical applications are impeded by challenges such as low ionic conductivity, uncontrolled Li-dendrite growth, and interfacial instability. This study presents a scalable strategy to address these limitations by incorporating ferroelectric BaTiO₃ into poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (PVDF-HFP) nanowebs. The 3D nanowebs were utilized to prepare composite solid polymer electrolytes (3DCSPEs), which exhibited significantly higher ionic conductivity (8.5 × 10^-4 S cm^-1 at 25 °C) and a higher Li-ion transference number (0.78) than a PVDF-HFP-based solid polymer electrolyte (PSPE). The 3DCSPEs effectively regulated Li-ion flux, suppressed dendrite growth, and stabilized interfacial contact. In battery tests, LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811)/3DCSPE/Li cells outperformed conventional NCM811/PSPE/Li cells, exhibiting a higher capacity (143.72 mA h g^-1 at 0.1 C) and superior prolonged cycle stability over 600 cycles at 0.2 C at 25 °C. Additionally, 3DCSPE mitigated cathode cracking and enhanced ion transport, demonstrating its potential to advance Li polymer battery technology. This study clarifies the pivotal role of <i>in situ</i> cross-linked ferroelectric 3D nanowebs as a novel approach for addressing the key challenges in ASSLBs, facilitating the development of advanced Li polymer batteries.