In-situ grown nickel selenide nanoparticles on carbon nanotubes for high performance flexible micro supercapacitors

The advancement of flexible and efficient energy storage devices is critical for next-generation portable electronics. In this work, we report the in-situ growth of nickel selenide (NiSe) nanoparticles over multi-walled carbon nanotubes (MWCNTs) to fabricate a high-performance flexible micro-supercapacitor (MSC) via a screen-printing technique. A novel conductive ink was formulated using NiSe/MWCNT nanocomposites and an eco-friendly binder system composed of cellulose acetate propionate and diacetone alcohol. The ink exhibited excellent thixotropic behaviour, ensuring optimal printability and film uniformity on PET substrates with silver current collectors. The fabricated symmetric MSC delivered a high areal capacitance of 321.9 at a current density of 0.5 and retained 93.3% of its initial capacitance after 5000 charge/discharge cycles. Furthermore, the asymmetric MSC (NiSe/MWCNT//AC) exhibited an outstanding areal capacitance of 478.9 and excellent cyclic stability. The synergy between the pseudocapacitive behaviour of NiSe and the high conductivity and surface area of MWCNTs significantly improved the electrochemical performance. This cost-effective and scalable screen-printing approach demonstrates strong potential for practical applications in wearable and flexible energy storage devices.