Engineered morphologies of β-NiS thin films via anionic exchange process and their supercapacitive performance

• The different nanostructures of β-NiS thin films developed using simple chemical anion exchange process.
• The stacked nano-needles based β-NiS thin film (NiS2) exhibit excellent electrochemical features.
• The β-NiS thin film based symmetric FSS-SCs device glows 40 red LEDs for 45 s, after charging for 30 s.

This effort dispenses an unprecedented electrochemical performance of highly porous nano-needles, stacked nano-needles, nano-plates and nano-flowers like morphological β-NiS thin films, synthesized through an anion exchange process using hydrothermally prepared Ni(OH)2 thin films. The stacked nano-needle structured β-NiS thin film shows maximum specific capacitance (Cs) of 415.78 Fg− 1 at current density of 0.5 mA cm− 2 in 2 M KOH electrolyte with electrochemical stability up to 91% after 2000 cyclic voltammetry (CV) cycles. In addition, symmetric flexible solid state supercapacitor (FSS-SCs) device fabricated using β-NiS thin films and polyvinyl alcohol-lithium perchlorate (PVA–LiClO4) as a polymer gel electrolyte, shows acceptable Cs of 55.83 Fg− 1 at scan rate of 10 mV s− 1 within operating potential window of 1.2 V. The symmetric FSS-SCs device manifests maximum specific energy density of 9.30 Wh kg− 1 and specific power density of 666 W kg− 1 along with better electrochemical stability of 90% after 1500 CV cycles. More interestingly, symmetric FSS-SCs device easily light up the panel of 40 red light emitting diodes (LEDs) texted as ‘CDL’ for 45 s after charging for 30 s.

The schematic of NiS formation on SS substrate with different steps of anion exchange process. The inset shows actual demonstration of fabricated symmetric flexible solid state supercapacitor (FSS-SC) device by glowing the 40 LED's texted as ‘CDL’.Figure optionsDownload as PowerPoint slide