Engineering heterostructured nickel–cobalt sulfide@hydroxide nanoarrays with spontaneous and fast interfacial charge transfer for high-energy-density supercapacitors

In this work, a heterostructured electrode based on a nickel-cobalt sulfide@nickel-cobalt layered double hydroxide (NCS@NC LDH) core-shell nanoarray is fabricated using a three-step hydrothermal strategy, which has the advantages of high mass loading (over 8.1 mg cm-2), an open structure, fast charge transfer capability and low ion diffusion resistance. Experimental analyses and theoretical calculations confirm that heterostructured NCS@NC LDH can induce spontaneous and rapid charge transfer from the shell to the core and improve the ion storage capability of the electrode. As expected, the designed electrode boosts the specific capacitance to an ultrahigh value of 16.3 F cm-2 (2010 F g-1) at 1 mA cm-2, which is approximately 2.14 times and 8.36 times those of NiCo2S4 and the Ni-Co layered double hydroxide. In addition, the assembled asymmetric supercapacitor shows a high areal energy density of 880 mu W h cm-2 (108.8 W h kg-1) under a power density of 1.5 mW cm-2 and long-term cycling stability. This work demonstrates an efficient strategy for realizing high-energy-density supercapacitors via electrode interface design. The electrodes of NCS@NC LDH core-shell nanoarrays have high mass loading and superior conductivity of which the assembled asymmetric supercapacitor demonstrates a high energy density of 880 mu W h cm-2 (1.5 mW cm-2).