Fiber Electrodes Mesostructured on Carbon Fibers for Energy Storage
Jisu Kim, Jin Gu Kang, Jaewon Choi, Paul V. Braun, Sung‐Kon Kim
Abstract
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).