Development of a spread-tow fabric composite bipolar plate with fiber-spreading effect for vanadium redox flow battery

This study investigates a spread-tow fabric carbon/epoxy composite as an alternative to graphite bipolar plates in vanadium redox flow batteries. A spread-tow fabric composite can leverage the electrical and mechanical properties of conventional unidirectional and densely woven fabrics. Spread-tows can reduce the morphological effect of fiber tows on both properties by minimizing the height variation in the fabric and the generation of crimps, referred to as the fiber-spreading effect. The developed spread-tow carbon/epoxy composite bipolar plate with a 10 k spread-tow exhibited an area-specific resistance similar to that of a unidirectional fabric and lower than that of conventional 1 k and 3 k woven fabric composites. Furthermore, the tensile strength reached 762 MPa, approximately 85% higher than that of the unidirectional fabric composite. The spread-tow bipolar plate specimen demonstrated gas tightness for 100 h and achieved an energy efficiency of 81.18% without any damage or degradation during single-cell charge/discharge tests.