Abstract: Structural batteries integrate load-bearing and energy storage functions simultaneously, delivering high energy density, outstanding mechanical properties and lightweight merits, which endows them promising application prospects in electric vehicles and aerospace industries. However, the structure-performance correlation between glass fiber fabric parameters and electro-mechanical behaviors of structural batteries remains unclear. This work systematically investigates four glass fiber textiles namely 1080, SW80, SW110, SW210 as structural separators. The results demonstrate that fiber chemical composition dominates electrolyte wettability. HS-glass based SW-series fabrics present superior wettability compared with D-glass based 1080 fabric, achieving contact angles of 22.42–23.99° at 40 ms and complete wetting within 200–360 ms. Owing to the thin thickness and twill weave structure, SW80 delivers the highest porosity of 62.72%, endowing optimized Li⁺ transport with low impedance of 2.50 Ω and high ionic conductivity of 1.59 mS cm⁻¹. The structural battery with SW80 separator and carbon fiber current collector achieves a high discharge specific capacity of 136.99 mAh g⁻¹ and an energy density of 37.57 Wh kg⁻¹, maintaining a capacity retention of 78.68% after 100 cycles at 0.1 C. Meanwhile, the integrated composite possesses excellent mechanical performance with a tensile strength of 261.60 MPa and a Young’s modulus of 20.65 GPa. This work clarifies the electro-mechanical structure-performance relationship and provides a feasible guideline for high-performance structural battery separator design and selection.