Effect of interlayer stitching in thermoplastic composite-packaged structural battery on electrochemical performance under mechanical loads

Structural batteries are multifunctional systems that integrate mechanical load-bearing capabilities with energy storage functions. However, conventional polymer matrices used in composite materials exhibit poor oxygen and moisture barrier properties, compromising electrolyte stability. To address this issue, a selective encapsulation strategy was implemented using a liquid thermoplastic polymer and masking techniques. A polypropylene barrier, recognized for its superior moisture and oxygen resistance, was selectively integrated around the electrode regions, while a thermoplastic polymer was applied to the external layers. This advanced design significantly enhanced electrolyte protection. One of the primary challenges in structural battery design is the weak interfacial adhesion between current collectors, electrolyte layers, and separators, which can lead to delamination, increased internal resistance, and reduced charge transfer efficiency. To mitigate these issues, a stitching reinforcement strategy was employed, minimizing electrode spacing between the cathode and anode to optimize ion transport pathways. In a static structural battery, the incorporation of a stitching architecture resulted in up to a 13 % increase in energy density compared to the non-stitched configuration. The stitching architecture effectively maintained a narrow electrode spacing between the cathode and anode under mechanical loads, significantly enhancing capacity retention. The proposed structural battery exhibited a tensile strength of 189 MPa and a tensile modulus of 9.1 GPa, achieving an energy density of up to 39.5 Wh/kg based on the total mass of the structural battery. These findings underscore the substantial potential of stitched structural batteries in high-performance applications, providing an innovative approach to improving both mechanical integrity and electrochemical efficiency in multifunctional energy storage systems.