Abstract: Solid-state lithium metal batteries, featuring inherent safety and ultra-high energy density, represent a key research direction in the field of energy storage. Polyethylene oxide (PEO)-based solid polymer electrolytes possess excellent interfacial compatibility and film-forming performance, while their low ionic conductivity and poor mechanical properties greatly limit their practical applications. To solve these problems, a synergistic reinforcement system composed of strontium titanate (SrTiO₃, STO) nanoparticles and hyperbranched poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibers is constructed. A bioinspired three-dimensional hyperbranched fiber framework is fabricated via turbulent shear-induced phase separation, and a composite solid electrolyte (CSE) is further prepared through an aqueous solution casting process. Scanning electron microscopy (SEM) and electrochemical tests are performed to characterize the material properties. The results indicate that the three-dimensional fiber network can provide continuous lithium-ion transport pathways, and high-dielectric STO may promote lithium salt dissociation via local dielectric fields and anchoring free anions. The optimized electrolyte delivers an ionic conductivity of 2.66×10⁻⁴ S·cm⁻¹ at 50℃, a lithium-ion transference number of 0.35, a tensile strength of 7.6 MPa, and an electrochemical stability window of 4.6 V. Assembled with a lithium iron phosphate cathode and a lithium metal anode, the battery achieves a discharge specific capacity of 161.6 mAh·g⁻¹ at 0.2 C and retains 98% of its initial capacity after 150 cycles. This structural regulation strategy provides a feasible preparation process with low equipment requirements and scalability potential for high-performance solid electrolytes.