Reverse voltage pulse deposition of a porous polyaniline/Mn–Co sulfide composite cathode material for modified Zn-ion hybrid supercapacitors

Abstract

For the purpose of expanding the working potential window and reducing the self-discharge for a Zn-ion hybrid supercapacitor, a positive electrode (cathode) of the Mn–Co-sulfide–polyaniline (MCS–PANi) composite coated on porous graphite paper was prepared using the reverse voltage pulse electrodeposition method. The electrode first achieved a high specific capacitance of 1048.8 F g⁻¹ at a scan rate of 5 mV s⁻¹ in the 1 M ZnSO₄ and 0.1 M MnSO₄ electrolyte solution. The Zn negative electrode (anode) was modified by organic fatty alcohol additives to reduce oxidation and dendrite growth. A hydrophilic modified polypropylene (PP) nonwoven fabric was used as a separator. The MCS–PANi-Zn-ion hybrid supercapacitor (MPZHSC) exhibited a very wide potential window of 2 V in aqueous electrolytes, a high specific capacitance value of 586.7 F g⁻¹ at a scan rate of 5 mV s⁻¹, an excellent durability of 98.3% after 11 232 cycles and a low self-discharge rate, retaining over 60% of its initial voltage value after 7 days. In addition, a device with a small active area of 2 cm² can be used to light a 2.5 W LED module for about 15 min, suggesting MPZHSC's potential practical applications.