Facile synthesis of NiAl layered double hydroxide nanoplates for high-performance asymmetric supercapacitor

NiAl layered double hydroxide (NiAl-LDH) is a promising electrode material for supercapacitor owing to its versatility in compositions, high theoretical capacitance, environmental benignity, and low cost. However, capacity fading of NiAl-LDH hinders its application in energy storage. Herein, we develop a facile hydrothermal approach to synthesize NiAl-LDH nanoplates (H-NiAl-LDH) possessing high electrochemical activity and desirable morphology to improve ion diffusion kinetics and reduce charge transfer resistance, leading to enhanced specific capacitance compared to pristine NiAl-LDH (P-NiAl-LDH) grown by co-precipitation method. Scanning electron microscopy shows that the H-NiAl-LDH are as thin as ∼30 nm with a mean lateral dimension of ∼150 nm. The H-NiAl-LDH electrode delivers remarkably high specific capacitance of 1713.2 F g−1 at 1 A g−1 and good cycling ability of 88% capacitance retention over 5000 cycles compared to only 757.1 F g−1 at 1 A g−1 and 76.4% of the P-NiAl-LDH. An asymmetric supercapacitor (ASC) is assembled using H-NiAl-LDH and graphene as positive and negative electrodes, respectively. The ASC operating at 1.4 V delivers a high specific capacitance of 125 F g−1 at 1 A g−1 with a high energy density of 34.1 Wh kg−1 at a power density of 700 W kg−1 and outstanding cyclic stability of 91.8% capacitance retention after 5000 cycles.