CoNi-layered double hydroxide array on graphene-based fiber as a new electrode material for microsupercapacitor

Fiber-shaped supercapacitors (FSSCs) have attracted increasing interest owing to their advantages of lightweight, high flexibility and tiny volume. However, the practical application of FSSCs is still obstructed by their relatively low energy density and poor cycling stability. Herein, we report the design and fabrication of a well-aligned hollow fiber electrode via a two-step procedure, which involves the preparation of reduced graphene oxide (RGO) hollow fibers in capillary glass tubes and following in situ electrodeposition of CoNi-layered double hydroxide (LDH) nanoplate arrays on RGO. The resulting RGO@CoNi-LDH fiber electrode displays excellent electrochemical performance including high capacitance (570 mF cm⁻²) and good cycling stability (95.3% retention after 2000 cycles), as well as admirable mechanical property and wearable capability. By using this hollow fiber as positive electrode, a flexible all-solid-state asymmetric FSSCs was further obtained, which shows high energy density (8.89 μWh cm⁻² at power density of 0.525 mW cm⁻²) and long-term bending durability. The energy and power densities are in the highest level among those of the reported FSSCs. Therefore, this work provides a new method for the construction of hybrid fiber electrodes for high-performance microsupercapacitors, which show a broad application prospects in next-generation wearable electronics.