Structural engineering and surface modification of nickel double hydroxide nanosheets for all-solid-state asymmetric supercapacitors

Metal chalcogenides' unique physical and chemical features, such as metal sulfides and selenides, have received significant attention as attractive materials for supercapacitor (SC) applications. Metal chalcogenides have better electrical conductivity, excellent thermal and mechanical stabilities than corresponding metal oxides and hydroxides. In this work, monocrystalline Ni-M (M = Se, S, P, O) nanosheet (NS) on Ni-foam's surface were prepared as binderless electrodes (positive) for asymmetric SCs (ASC). The NiSe2 NS, a hierarchical 3D nanostructure with abundant active sites, showed the best performance among the differently prepared metal chalcogenides. After 10,000 cycles, NiSe2 NS exhibited a superior capacity of 4.2 mAh cm(-2) with 66.7% rate capability and cycling stability of 92.7%. A negative electrode, profoundly exfoliated iron titanium nitride at graphene aerogel doped with nitrogen (Fe-TiN@NG), was also fabricated in this work for SCs applications. The constructed ASC device delivers 1.6 V (maximum operating voltage), a remarkable volumetric capacity of 2.1 mAh cm(-3) @ 3 mA cm(-2), a superior energy and power densities of 85.1 W h Kg(-1), 516.3 W Kg(-1), with 91.3% of capacity retention after 15,000 cycles. Such results can be used as a guideline for preparing SCs with high energy density and high stability.