LAUSR

Abstract Asymmetric fiber supercapacitor (AFSC) is one of the most promising options to boost the energy density for wearable energy storage. In conventional ASCs, the mass matching is normally used to achieve a charge balance between positive and negative electrodes, which would cause different lengths of fiber electrodes that lowers the energy density and bottlenecks the practical use of AFSC devices. The length matching between two electrodes is of vital importance for the practical use of high-energy AFSCs and has all along been overlooked. In this work, using engineered activated carbon fiber (ACF) as a substrate, we fabricate a robust polyaniline (PANI) composite fiber electrode (PANI@Ink/ACF) with a high length capacitance of 108 mF cm−1 (688 mF cm−2), which can be used as the negative electrode to couple with our previously reported MnO2@Ink/ACF composite fiber with the same length. Benefiting from the length matching strategy, the assembled AFSC device delivers an exceptional energy density of 16 μW h cm−1 (102 μW h cm−2), which is among the highest values reported. This work suggests a practical way to realize high-energy AFSCs, and holds great promise to integrate AFSCs with the well-established weaving technology of carbon fibers for wearable electronics.