Property Evaluation of Hybrid Vehicle Auxiliary Battery Cases Using Lightweight Polymer Nanocomposites

With the rapid advancement of vehicle electrification and the increasing integration of electronic systems, electromagnetic interference (EMI) has emerged as a critical issue affecting the reliability and safety of automotive electronics. In hybrid vehicles, low-voltage auxiliary batteries supply stable power to electronic control units and onboard electrical systems, requiring battery cases that simultaneously provide effective EMI shielding, high mechanical strength, lightweight characteristics, and good processability. In this study, Nylon 6 (polyamide 6)-based carbon nanocomposites were developed as lightweight EMI-shielding materials to replace conventional aluminum auxiliary battery cases. Multi-walled carbon nanotubes (MWCNTs), carbon black (CB), and graphene nanoplatelets (GNPs) were incorporated with a total filler loading of 10phr, and the effects of filler composition and dispersion on the electrical, mechanical, rheological, and thermal properties of the composites were systematically investigated. The optimized nanocomposite exhibited a surface resistivity of 10³–10⁴Ω/□ and a tensile strength exceeding 70MPa while maintaining shear-thinning behavior suitable for injection molding. Furthermore, a prototype battery case fabricated using the optimized composite achieved more than 54% weight reduction compared with conventional aluminum cases while satisfying automotive environmental and durability requirements. These results demonstrate the strong potential of polymer-based carbon nanocomposites for lightweight EMI shielding applications in automotive battery systems.