3D Architecture Materials Made of NiCoAl-LDH Nanoplates Coupled with NiCo-Carbonate Hydroxide Nanowires Grown on Flexible Graphite Paper for Asymmetric Supercapacitors

Asymmetric supercapacitors featuring both high energy and power densities as well as a long lifespan are much sought after and may become a reality depending on the availability of cheap yet highly active electrode materials. Here, a novel flexible architecture electrode made of NiCoAl-layered double hydroxide (NiCoAl-LDH) nanoplates coupled with NiCo-carbonate hydroxide (NiCo-CH) nanowires, grown on graphite paper via an in situ, one-step, hydrothermal method is reported. The nanowire-like NiCo-CH species in the nanoplate matrix function as a scaffold and support the dispersion of the NiCoAl-LDH nanoplates, resulting in a relatively loose and open structure within the electrode matrix. Asymmetric supercapacitors fabricated using the nanohybrids as the positive electrode and a typical activated carbon (AC) as negative electrode show a high energy density of 58.9 Wh kg(-1) at a power density of 0.4 kW kg(-1), which is based on the total mass of active materials at a voltage of 1.6 V. An energy density of 14.9 Wh kg(-1) can be retained even at a high power density of 51.5 kW kg(-1). Our asymmetric supercapacitor also exhibits an excellent long cycle life, whereby a specific capacitance of 97% is retained even after 10 000 cycles.