Enhanced ordered growth of Ni-Co LDH nanosheets on N-doped carbon through nitrogen configuration tuning for high-performance asymmetric supercapacitors

The introduction of carbon is considered a promising strategy to improve the cycling stability of Nickel-cobalt layered double hydroxide (NC-LDH) in supercapacitors. While, the construction of uniform and strong interface bonding is a major challenge for this strategy. Herein, a pyridinic N enriched carbon (PNC) is prepared by simple heat treatment of popcorn to adjust the nitrogen configuration and used as a substrate to load NC-LDH. The pyridinic N is favored to form chemical bonds of N-O-Ni/Co with NC-LDH and enhance the ordered growth of NC-LDH on the PNC surface. This unique NC-LDH/PNC hybrid benefits much more active sites and improved structure stability. Furthermore, the electrical conductivity and charge transfer ability are significantly enhanced due to the sufficient coupling between NC-LDH and PNC. As a consequence, the NC-LDH/PNC demonstrates a much higher capacitance of 877.5C/g (2193 F g- 1) at 1 A g- 1 and an enhanced rate of 62.4% at a greater current density of 20 A g- 1 compared with those of NC-LDH (624.5C g- 1 and 48.3 %). The NC-LDH/PNC-based asymmetric supercapacitor (ASC) obtains a remarkable specific capacitance of 343 F g- 1 at 1 A g- 1 and energy density of 121.9 Wh kg- 1 at 798.2 W kg- 1. More importantly, this NC-LDH/PNC based ASC exhibits significantly enhanced cycle stability of 90.2 % after 4000 cycles, compared with that of NC-LDH-based ASC (56.5 %).