Ni-Co sulfide hollow nanoboxes with enhanced lattice interfaces for high performance hybrid supercapacitors

Abstract

Bimetallic sulfides have been suggested as a novel class of electrode materials for supercapacitors (SCs) due to their high conductivity, rich redox active sites and wide operating potential window. To improve the property, tremendous efforts have been devoted to controlling the morphology, structure and size of bimetallic sulfides. We report here a strategy to achieve Ni-Co sulfide hollow nanoboxes with rich lattice interfaces and widespread mesopores via ion-exchange process. The lattice interfaces in the nanoboxes play a key role in improving the performance by developing more active sites. The thin nano-shell with porous structure makes it highly permeable for efficient ion diffusion, yet shortens the electron transport pathway. Such synergistic effects endow the Ni-Co sulfide hollow nanoboxes with high specific capacity of 789.0 C g−1 at 1 A g−1 and excellent rate capability of 82.1% capacity retention at 20 A g−1. Quantitative analysis of capacitive contribution sheds light on the rapid charge-discharge kinetics. Additionally, the as-fabricated hybrid SC, using optimized Ni-Co sulfide (Ni/Co molar ratio: 1/1) as anode and active rice husk carbon as cathode, exhibits a high energy density of 46.7 Wh kg−1 at power density of 400 W kg−1 and remarkable cycling stability of 82.7% at 5 A g−1 after 10,000 cycles, demonstrative of potential application for high-performance SCs.