Construction of nickel/cobalt encapsulated by N-doped carbon nanotubes for high performance supercapacitors

Armour-like nanomaterials could maintain high activity and stability under harsh conditions. In this paper, armour-like electrode material, Ni/Co encapsulated by N-doped carbon nanotubes (NCNTs-Ni/Co), are prepared with NiCo prussian blue analogue (PBA) as precursor and template. In particular, the NCNTs-Ni/Co formed at a C3H6 flow rate of 0.2 L min−1 exhibited a high length-diameter ratio and excellent supercapacitor performance. The specific capacitance at 1 A g−1 reached 231.2 F g−1 and the retention rate at 20 A g−1 was 69 %. The asymmetric supercapacitor (ASC) assembled from NCNTs-Ni/Co/0.2 and activated carbon (AC) exhibited a power density of 38.3 Wh kg−1 at 800 W kg−1 and retained the highest specific capacitance of 87.3 % after 10,000 charge/discharge cycles. In general, this study gives a new idea for the derivation of structures with excellent electrochemical performance and unique structure from PBA. [Display omitted] •NCNTs-Ni/Co is derived from thermal decomposition of NiCo PBA in C3H6 atmosphere.•NCNTs-Ni/Co consists of N-doped Carbon Nanotubes encapsulated Ni/Co.•The high flow rate of C3H6 tend to cause increase in the diameter of carbon nanotubes.•NCNTs-Ni/Co exhibits a high specific capacitance of 231.2 F g−1.•The asymmetric supercapacitor yields a maximum energy density of 38.3 Wh kg−1.