Silver Nanowires@Mn3O4 Core-Shell Nanocables as Advanced Electrode Materials for Aqueous Asymmetric Supercapacitors

High-electrical-conductivity silver nanowire (AgNW)@Mn3O4 nanocables are prepared by facile chemical precipitation and subsequent thermal treatment; these treatments are environmentally friendly, low cost, and easy for mass production. The obtained Mn3O4 nanoparticles (20-30 nm) possess many interparticle mesoporous structures. The AgNW-supported Mn3O4 nanoparticles allow for a large exposed electroactive area, rapid ion and electron transport, and robust structural stability. In addition, it is shown that the AgNWs play a positive role in the electrochemical properties of the Mn3O4 electrode used in a supercapacitor. The AgNW@Mn3O4 electrode delivers ultrahigh specific capacitances of 203 and 111 Fg(-1) at 0.25 and 2 Ag-1, respectively. When matched with the activated carbon (AC) anode, the AgNW@Mn3O4//AC asymmetric supercapacitor (ASC) device has a wide voltage window of 1.8V, a specific capacitance of 105 Fg(-1) at 1 Ag-1, and 94% capacitance conservation after 5000 cycles. Moreover, the aqueous ASC device exhibits an energy density of 28 Whkg(-1) (power density of 320 Wkg(-1)), and maintains a value of 10 Whkg(-1) as the power density increases to 9500 Wkg(-1), demonstrating potential for applications.