Fiber Electrodes Mesostructured on Carbon Fibers for Energy Storage

Herein, we demonstrate the formation of fiber electrodes on a carbon fiber (CF) bundle with a surface that is mesostructured by single-walled carbon nanotubes via colloidal self-assembly. The three-dimensional ordered structure of the fiber electrodes (M-CNT@CF) provides porosity and bicontinuous paths for charge transport, resulting in high energy and considerable rate retention capability as compared with nonstructured CF and CNT-coated CF electrodes. A fiber micro-supercapacitor (f-MSC) composed of a twisted pair of fiber electrodes with a solid polymer electrolyte shows significant capacitance (355 mF cm-3), rate retention capability (92% of low-current capacitance), and considerable cycle stability (99% retention of initial capacitance) for at least 7000 charge-discharge cycles and even under severe mechanical stress. In particular, M-CNT@CF is a promising template for active materials experiencing a Faradic reaction, such as manganese oxide (MnO2). As an added benefit of MnO2 plating, the capacitance of the resulting hybrid fiber electrodes (MnO2@M-CNT@CF) is 6.6 times greater than that of M-CNT@CF. This also demonstrates that the MnO2 plating significantly contributes to performance improvement when applied to the mesostructured electrode (M-CNT@CF) rather than a nonporous material (CF).