In-situ transformation of Ni foam into sandwich nanostructured Co1.29Ni1.71O4 nanoparticle@CoNi2S4 nanosheet networks for high-performance asymmetric supercapacitors

[Display omitted] •A new electro-oxidation method was explored to synthesize lamellar NiOOH.•The multi-dimensional Co1.29Ni1.71O4@CoNi2S4 networks were transformed from NF.•The nanosheets possess large interface and efficient conductive network.•The nanosheet network displays high capacitance and outstanding rate capability. Sandwich nanostructured networks constructed by cross-linked Co1.29Ni1.71O4@CoNi2S4 heterogeneous nanosheets in-situ generated on nickel foam are first synthesized through an innovative Fast-Repeated-Charging/Discharging (FRCD) electro-oxidation and subsequent ion-exchange. This multi-dimensional nanostructure assembled by 0D Co1.29Ni1.71O4 nanoparticles with the size of 10 ∼ 20 nm, 2D ultra-thin CoNi2S4 nanosheets with the thickness of about 1.5 nm and 3D interconnected nanosheets can endow the electrode material with abundant active sites, sufficient electrolyte-electrode interfaces, fast ion transport path, high conductivity and excellent structural stability to achieve remarkable electrochemical performance. Benefiting from this intriguing structural and componental advantages, the Co1.29Ni1.71O4@CoNi2S4 delivers ultra-high area specific capacity of 916 µAh cm−2, the area specific capacitance of 8386 mF cm−2 and the specific capacitance of 2045 F g−1 at 2 mA cm−2, and topping rate capability of 50.9% for capacity (91.1% for capacitance) from 2 to 200 mA cm−2. The fabricated Co1.29Ni1.71O4@CoNi2S4/NF//AC ACS exhibits a prominent energy density of 47 Wh kg−1 at 527 W kg−1 and possesses immensely distinguished cycling stability of 85.3% retention after 8000 cycles. Subsequently, the assembled Co1.29Ni1.71O4@CoNi2S4/NF//AC all-solid-state ASC device with a voltage window of 1.6 V delivers a high energy density of 44.3 Wh kg−1 at a power density of 496 W kg−1. This construction of advanced nanostructures will shed hoping light on designing high performance electrode materials for supercapacitors, batteries, water splitting and N2 reduction reaction.