Hierarchical ultrathin NiAl layered double hydroxide nanosheet arrays on carbon nanotube paper as advanced hybrid electrode for high performance hybrid capacitors

To effectively improve the power density and rate capability of layered double hydroxide (LDH) based supercapacitors, a hybrid supercapacitor (HSC) comprising of hierarchical ultrathin NiAl-LDH nanosheet arrays on carbon nanotube paper (CNP-LDH) is developed with porous graphene nanosheets as the negative electrode for the first time. SEM image shows that hierarchical NiAl LDH nanosheet arrays are assembled by numerous ultrathin nanosheets with thickness of a few to tens of nanometers. Remarkably, with an operating voltage of 1.6 V, the HSC possesses a high energy density of 50.0 Wh kg-1 at an average power density of 467 W kg-1. Even at a fast discharging time of 3.9 s, a high energy density (23.3 Wh kg-1) could also be retained at a power density of 21.5 kW kg-1. Moreover, the HSC exhibits cycling stability with a retention rate of 78% after 5000-cycle charge-discharge test at 5 A g-1. The results inspire us to propose our high-performance CNP-LDH as a promising electrode for energy storage applications.