Ni-Co-S/Co(OH)(2) nanocomposite for high energy density all-solid-state asymmetric supercapacitors

Rational design and synthesis of hybrid structures consisting with multiple pseudocapacitive components are challenging to develop materials with a high energy density for conversion and storage applications. Herein, a novel and cost-effective two-step method has been developed to synthesize three-dimensional (3D) nickel cobalt sulfides (Ni-Co-S)/Co(OH)(2) nanocomposite with synergistic effect to provide an excellent comprehensive electrochemical performance, which shows a high specific capacitance (1560.8 Fg(-1) at 1 A g(-1)) and outstanding rate capability (953.3 Fg(-1) at 30 A g(-1)). Subsequently, an all-solid-state asymmetric supercapacitor (ASC) was successfully assembled using Ni1-Co2-S/Co(OH)(2) nanocomposite as the positive electrode, activated carbon (AC) as the negative electrode and an alkaline PVA gel (PVA/KOH) as electrolyte. The Ni1-Co2-S/Co(OH)(2)//AC all-solid-state ASC device with a voltage window of 1.6 V delivered a maximum energy density of 48.8 W h kg(-1) at a power density of 800 W kg(-1) with excellent cycle stability. Excitedly, two all-solid-state ASCs assembled in series under fully charged can effectively light up four parallel connected light-emitting diodes (LEDs) for around 10 min, and can power a white LED (working voltage, 3.0-3.4 V) effectively. These remarkable electrochemical performances of Ni1-Co2-S/Co(OH)(2)//AC are beneficial to their practical applications for high-performance energy storage.