Dual-Network Synergistic Reinforcement toward Lightweight and High-Strength Flexible Graphite Bipolar Plates for Robust and Efficient Fuel Cells

Abstract The advancement of fuel cell technology plays a pivotal role in the development of hydrogen energy. Bipolar plates are important components of fuel cells. Developing flexural bipolar plates with stable mechanical properties and high conductivity addresses the critical need for improved power density and reduced system cost in fuel cells. In this study, we introduce a novel expanded graphite-carbon fiber/resin composite bipolar plate fabricated via hot-press molding. The plate is designed based on a dual-network synergistic reinforcement strategy, comprising a conductive graphite network and a mechanical carbon-fiber skeleton. During molding, the flowing resin bridges these two networks, enabling simultaneous enhancements in electrical conductivity and mechanical strength. This composite achieves a low density of 1.64 g/cm3, while exhibiting a high in-plane electrical conductivity of 393.70 S/cm, an effective through-plane conductivity of 7.538 S/cm, and a high flexural strength of 520.3 MPa at a minimal thickness of ∼0.6 mm. Furthermore, it fulfills critical operational requirements such as creep resistance, corrosion resistance, low surface roughness, and tunable hydrophobicity. To evaluate its practical energy utilization efficiency, we compared the power of various composite bipolar plates under sustained load conditions. This comparison confirmed the robustness of the prepared composite bipolar plates in withstanding mechanical stresses, revealing their potential in practical fuel cell applications.