Interfacial engineering of Ag nanoparticle-decorated polypyrrole@Co(OH)2 hetero-nanostructures with enhanced energy storage for hybrid supercapacitors

Battery-type electrode materials (BTEMs) still suffer from unsatisfactory actual specific capacities and cycling stability, which impede their applications in hybrid supercapacitors (HSCs). Herein, we report an interfacial engineering strategy to improve the energy storage performance of Co(OH)2-based BTEMs by constructing the polypyrrole (PPy)@Co(OH)2 @Ag hetero-nanostructures (HNs). In such HNs, Co(OH)2 nanosheets are initially grown onto PPy nanowires on Ni foam, which offer rich electroactive sites, efficient charge transport, and good mechanical stability. More importantly, density functional theory (DFT) calculation results indicate that the subsequent decoration of Ag NPs on Co(OH)2 nanosheets provides an enhanced electrical conductivity as well as a reduced surface adsorption energy of OH- at Co(OH)2 nanosheets compared to the PPy@Co(OH)2 HNs without the decoration of Ag NPs. Consequently, the prepared PPy@Co(OH)2 @Ag electrode material demonstrates a specific capacity of up to 277 mA h g−1 at 2 A g−1, 72 % capacity retention at 20 A g−1 together with a 92 % capacity retention over 5000 cycles at 10 A g−1. Furthermore, a HSC device using the PPy@Co(OH)2 @Ag as positive electrode has been fabricated to achieve an energy density of 54.4 W h kg−1 at 800 W kg−1. This work provides a new insight into the structural design of BTEMs for their applications in HSCs.