Nitrogen-doped carbon nanotube supported double-shelled hollow composites for asymmetric supercapacitors

In this work, a unique N-C@NiMoO4 composite with a double-shelled hollow microtube structure has been developed through a simple and low-cost growth process. The composite contains a NiMoO4 outer shell with high electrochemical activity and hollow nitrogen-doped carbon nanotubes (N-C NTs) with high conductivity, resulting in a high performance electrode material. The existence of N-C NTs effectively prevents the accumulation and agglomeration of the NiMoO4 nanosheets during the formation of a uniform outer shell, providing a higher specific surface area (258.2 m(2) g(-1)). The electrochemical study displays that the C@NiMoO4 composite has a specific capacitance as high as 1242 F g(-1) at a current density of 1 A g(-1), and about 82.9% cycling stability after 2000 cycles. Moreover, the as-fabricated C@NiMoO4//N-C asymmetric supercapacitor (ASC) can achieve a maximum high energy density of 44.6 W h kg(-1) at a power density of 250.4 W kg(-1). These results imply that the C@NiMoO4 composite with a double-shelled hollow tube-structure is a promising candidate for high performance supercapacitors.