“Gel‐in‐Resin” Multifunctional Electrolytes for Enhanced Electrochemical and Mechanical Performance in Lithium‐Ion Structural Battery Composites

Abstract Structural battery composites (SBCs) integrate mechanical load‐bearing capability with energy storage functions, offering potential for significant weight reduction. However, the commercial application of SBCs remains hindered by the trade‐off between electrochemical performance and mechanical properties. This study presents a novel dual‐phase Gel‐in‐Resin (GIR) electrolyte, comprising a PVDF‐HFP‐based gel embedded within a porous epoxy resin framework. The epoxy skeleton effectively bonds carbon and glass fabrics while providing adequate space for the gel electrolyte. Electrostatic interactions between succinonitrile groups and Li⁺ ions stabilize the electrochemical window (5.21 V) and enhance the Li‐ion transference number ( t Li ⁺ = 0.59), promoting the formation of a robust LiF/Li 3 N hybrid solid electrolyte interphase. The coupling of the epoxy resin and gel electrolyte improves mechanical properties, increasing the tensile modulus by 22%. Finite element modeling reveals that structural barriers and ion pathways within the epoxy framework restrict Li⁺ transverse migration and inhibit dendrite formation. As a result, lithium iron phosphate (LFP) || graphite SBCs with GIR electrolyte exhibit excellent electrochemical performance (120.43 mAh g −1 at 0.2 C) and exceptional cycling stability (81.44% retention after 180 cycles). This work provides a promising pathway for the development of high‐performance SBCs for practical applications.