Tailored Stitching and Vertical Stacking for High-Voltage Multifunctional Structural Batteries with Enhanced Electrochemical–Mechanical Coupling

Multifunctional structural batteries combining mechanical load-bearing and energy storage offer strong potential for lightweight systems. However, conventional carbon-fiber-reinforced polymer (CFRP)-based designs face persistent challenges including electrode delamination, inter-cell dead space, poor electrolyte stability, and insufficient interfacial bonding. This study introduces a CFRP-based, vertically stacked high-voltage structural battery that integrates through-thickness aramid fiber stitching with selectively structured thermoplastic interfaces. The system employs Elium resin and polypropylene barriers to enhance moisture and oxygen shielding while preserving mechanical integrity. Tailored stitching architectures are systematically investigated over a range of stitch densities, revealing their influence on both electrochemical impedance and interlaminar shear strength. The resulting structure exhibits an energy density of 42.2 Wh kg⁻¹ based on total structural mass, representing a 14% improvement over the unstitched configuration. Notably, the stitched architecture yields a flexural strength of 215.6 MPa and a modulus of 14.7 GPa, representing a 40% enhancement in mechanical properties over unstitched counterparts. This level of performance places the system among the most competitive structural battery designs reported to date in terms of multifunctional integration. Energy performance remains stable under mechanical deformation, significantly outperforming unstitched configurations in both electrochemical and structural resilience.