Mesoporous Ni-PANI composite electrode for electrochromic energy storage applications

Nanostructured mesoporous Ni-PANI thin film electrodes are fabricated on indium-doped tin oxide (ITO) conducting glass substrates using a pulse potential electro-polymerization technique. The Ni-PANI film is amorphous in nature and exhibits a mesoporous cauliflower like morphology. The multifunctional characteristics of Ni-PANI as an electrode for a smart supercapacitor are investigated using electrochemical and optical techniques in 0.5 M LiClO₄ +PC electrolyte. It is dark blue when it is charged at 0.7 V (vs SCE), and it is transparent when it is discharged at −0.7 V (vs SCE). Moreover, it can exhibit other colours like sky blue and parrot green in intermediate states. Specific discharge capacitance of 543 Fg⁻¹ and 267 Fg⁻¹ at a current density of 1 Ag⁻¹ is obtained for Ni-PANI and pure PANI respectively. The observed colouration efficiency is 45.9 cm²C⁻¹ for Ni-PANI and 35.1 cm²C⁻¹ for pure PANI at a wavelength of 630 nm. An outstanding optical modulation of 55.6% with a capacity retention of 90% after 5000 cycles is obtained for Ni-PANI electrode. The robust synthesis of Ni-PANI electrodes with efficient smart supercapacitor activity can be used as alternative materials in smart energy storage devices.