High stability and uniform Li deposition are essential for realizing applications of Li-metal batteries (LMBs). Therefore, a scaffold for polymer electrolytes is designed to achieve highly stable operation and dendrite-free Li deposition. A porous membrane of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) is synthesized as a scaffold to host a networked poly(ethylene oxide) (PEO)-based solid polymer electrolyte (NSPE) and form a scaffold-hosted electrolyte (NSPE@PF) that exhibits a considerably higher ionic conductivity and Li⁺-transference number at 30 °C than the reported PEO-based solid polymer electrolytes do. The PVdF-HFP scaffold renders the NSPE@PF electrochemically stable until 5.4 V (vs. Li/Li⁺). The PVdF-HFP membrane facilitates uniform Li deposition on both Cu- and Li-metal anodes with negligible dendrite growth in both solid-polymer and liquid electrolyte systems. LMBs containing the NSPE@PF exhibit high capacities and a high cycling stability of up to 1100 cycles. The high-dielectric feature of the PVdF-HFP scaffold facilitates counter-ion-pair dissociation and extends the stable voltage range. Its anion-tethering ability minimizes the space-charge zones on the Li-anode surface and suppresses Li-dendrite growth. Moreover, the high mechanical strength of the scaffold facilitates the synthesis of thin and practically usable NSPE@PFs. This scaffold design is promising for realizing LMB applications.