Rationally design nickel sulfide@PEDOT arrays as binder-free cathode for durable asymmetric supercapacitor and aqueous Ni–Zn battery

The practical energy storage applications of metal sulfides are greatly hindered by their unsatisfactory specific capacity, inferior rate capability and poor stability. In this work, monolithic Ni3S2@PEDOT arrays are rationally designed by surface engineering as robust binder-free cathode to boost the electrochemical performances of asymmetric supercapacitor and aqueous Ni–Zn battery. Benefiting from the unique protective and conductive PEDOT shell to accelerate the electron/ion transport and provide a large interfacial area, the monolithic Ni3S2@PEDOT array displays a ultrahigh reversible specific capacitance (1589.3 F g−1 at 2.0 A g−1) and favorable rate capability (75.5% of initial capacity retention under 10 A g−1). The assembled Ni3S2@PEDOT//active carbon asymmetric supercapacitor exhibits a remarkable capacity of 243.6 F g−1 at 0.5 A g−1 and outstanding cycling durability (only 2.4% decay within 4000 cycles). Moreover, the aqueous Ni3S2@PEDOT//Zn battery reveals an admirable specific capacity 261.9 mAh g−1 under 3.13 A g−1 while only reaching 2.7% capacity attenuation within 2000 cycles. Furthermore, the aqueous rechargeable Ni3S2@PEDOT//Zn battery presents an impressive energy density 456.4 Wh kg−1, together with a peak power density 5.45 kW kg−1. These encouraging results offer compelling insights for the design of high-performance metal sulfides and numerous electronics, electric vehicle applications in the future.