Robust and Conductive Polymer Electrolytes via Solvent‐Guided Hierarchical Network Formation

ABSTRACT Solid polymer electrolytes (SPEs) for lithium‐metal batteries (LMBs) confront an inherent trade‐off: mechanical robustness needed to suppress dendrite conflicts with ionic conductivity required for electrochemical performance. Conventional processing with strongly solvating solvents produces microspherical structures that isolate mechanical and ionic transport pathways, while strategies like ceramic fillers or gel formation improve one property at the expense of others. We resolve this dilemma through solvent‐interaction engineering that guides PVDF‐HFP through a controlled solution–gel–solid transition into hierarchically networked SPEs. Moderate‐solvency solvents trigger physical crosslinking at high concentrations, constructing macroscopically densified frameworks with continuous mesoscopic porosity and weakly bound microscopic solvation shells. The resulting SPE achieves 2.93 mS·cm −1 ionic conductivity alongside order‐of‐magnitude mechanical enhancements—modulus from 6.8 to 44.88 MPa, strength from 0.56 to 5.55 MPa, and fracture energy from 0.7 to 66.8 kJ·m −2 . Li||Li cells cycle stably for over 10 000 h, and Li||LiFePO 4 pouch cells retain 90.6% capacity after 200 cycles. This general approach reconciles mechanical integrity with electrochemical function across diverse solvent formulations.