All-solid-state printable supercapacitors based on bimetallic sulfide NiCo2S4 with in-plane interdigital electrode architecture

Fabricating flexible, solid, miniature and low-cost energy storage units has received growing attention as the rapid development of flexible electronic devices. Herein, we demonstrate the easy manufacturing of all-solid-state flexible supercapacitor with in-plane interdigital electrode architecture based on nickel–cobalt bimetallic sulfide NiCo 2 S 4 . With the help of a shadow mask printing technique, the NiCo 2 S 4 -based electrodes were printed on a flexible PET substrate using the home-made ink comprised of NiCo 2 S 4 , carbon nanotubes, PTFE and terpineol. Then a PVA-KOH gel electrolyte was coated and cured to complete the assembly of interdigital supercapacitor. The NiCo 2 S 4 electrode exhibits a high specific capacitance of 1401 F/g. After 3000 cycles, the capacitance retention maintains 90%, showing a remarkable cycle stability. The assembled interdigital device delivers a high specific areal capacitance of 13.6 mF/cm 2 at a current density of 0.35 mA/cm 2 and an excellent energy density of 2.1 μWh/cm 2 at a power density of 0.189 mW/cm 2 , with both long-term cycling and high rate stability. The electrochemical performance remained consistent at different bending angles (0°, 90° and 180°). This work demonstrates a simple and low-cost preparation of printable supercapacitor based on NiCo 2 S 4 interdigital electrodes, which has a great potential to be used for flexibility, wearable and portable devices. Graphical abstract