Imbuing carbon fibers with electrochemical storage properties without compromising fiber‐to‐matrix adhesion

The application of carbon fiber in structural batteries and capacitors may be advanced by increasing the surface functionality of these materials. Herein, we describe the electrochemical surface modification to attach ferrocene containing polymers to the carbon fiber surface. This was carried out using a ferrocene monomer in isolation, and as part of a blend in acrylamide. The ferrocene‐containing polymers significantly improve the interfacial shear strength (+180%) in an epoxy resin and improves the tensile strength of the fiber by more than 10%, compared to a control sample (modified fiber 3.81 ± 0.08 GPa; pristine fiber 3.56 ± 0.09 GPa, respectively). These polymers also improve the specific capacitance of the fiber (1250 mF g−1) compared to pristine (113 mF g−1). An excellent retention of capacitance (80%) was also found for these modified materials via galvanostatic charge–discharge stability tests after 1000 charge–discharge cycles.