Surface sulfidation of NiCo-layered double-hydroxide nanosheets for flexible all-solid-state fiber-shaped asymmetric supercapacitors

Flexible fiber supercapacitors have received much attention as emerging energy storage equipment for powering wearable electronics. Nonetheless, the small surface area of fiber substrate and poor reaction kinetics of active material lead to low specific capacitance and energy density, inhibiting its application in real life. Herein, a NiCo-layered double-hydroxide@hydroxysulfide (NiCo-LDH@HOS) fiber electrode with multi-component synergistic three-dimensional hierarchical structure is fabricated by rational design and surface sulfidation. NiCo-LDH derived from ZIF-67 provides large specific surface area and rich active sites. Surface sulfidation optimizes electronic structure of the active center, adjusts the ionic covalent nature of the original LDH, and enhances the reaction activity and electrical conductivity. Consequently, the rational designed NiCo-LDH@HOS fiber electrode displays high specific area capacitance of 1100 mF cm −2 at 2 mV s −1 in the three-electrode system. In addition, the flexible all-solid-state fiber-shaped asymmetric supercapacitor fabricated with NiCo-LDH@HOS and activated carbon showed a maximum energy density (44.37 μWh cm −2 at 7442.31 μW cm −2 ). Furthermore, the device delivers good cycling stability and flexibility, showing enormous potential for next-generation wearable electronics and smart textiles. Graphical abstract The mechanistic diagram of fiber-shaped all-solid-state ASC assembled with NiCo-LDH@HOS as cathode and AC as anode.