Nickel-cobalt layered double hydroxide fabricated on TiO2/C nanofiber arrays as free standing electrode for high performance supercapacitors

Nickel-cobalt layered double hydroxides (LDHs) as electrode materials have recently received intense interests. However, the low conductivity, sluggish charge transfer kinetics and poor electrolyte penetration restrict the capacitive performance and hinder their practical applications. Herein, the Ni-Co-LDH nanosheets were introduced to the core/shell structured TiO2/C nanofiber arrays (TiO2/C NFAs) to construct a free-standing composite electrode for supercapacitor through a one-step electrodeposition method. The best-performing Ni1Co1-LDH/TiO2/C NFAs electrode exhibits high specific capacitance (1717.8 F g−1 at 1 mA cm−2), remarkable rate capability with 75.1 % retention when the current density increased from 1 mA cm−2 to 75 mA cm−2, and excellent cycling stability (84.1 % of the original capacitance after 5000 cycles at 78.1 A g−1), surpassing most of the Ni-Co-LDH electrodes reported before. This excellent performance owes to the high conductivity of TiO2/C NFAs which can endow the low ohmic resistance and high diffusion coefficient of Ni-Co-LDH which may alleviate the structure degradation. Meanwhile, the Ni-Co-LDH with the optimized Ni/Co ratio of 1:1 can provide proper particle size of LDH nanosheets, small charge transfer resistance (Rct), and high stability of Ni-Co-LDH to resist the structure degradation in the long-term cycling process.