Synthesis of amorphous Nickel-Cobalt hydroxides with high areal capacitance by one-step electrodeposition using polymeric additive

[Display omitted] •Polymeric additive was introduced to the electrochemical synthesis of NiCo-OHs.•A transition of NiCo-OHs from crystalline phase to amorphous phase was achieved.•The NiCo-OH-SA3 exhibits a high specific capacitance of 9.0F cm−2 (2360F g−1).•The optimal synthesis condition is related to polymer’s overlap concentration. Nowadays, in order to gain high-performance supercapacitors with well-designed nanostructures, the preparation processes always possess sophisticated and time-consuming multiple steps. Here, we developed a facile and time-saving electrodeposition strategy to prepare amorphous nickel–cobalt hydroxides (NiCo-OHs) electrode with high areal specific capacitance by introducing polymers into the electrolyte. Polymer, with long chain, high solution viscosity and coordination effect, could induce a nondirectional growth of NiCo-OHs and form disordered structure with plentiful mesopores. After investigating the effects of polymers’ type and concentration on the growth process, amorphous NiCo-OHs with high mass loading were well anchored on the surface of carbon cloth. The amorphous phase and ample mesopores offer quantities of electrochemical active sites and high specific capacitance. The as-prepared amorphous NiCo-OHs electrode exhibits a highest areal capacitance of 9.0 F cm−2 at 2 mA cm−2, good rate capability with an areal capacitance of 4.5 F cm−2 at 50 mA cm−2 and long cyclic life (63% retention, 10,000 cycles). Moreover, the assembled asymmetric supercapacitor exhibits a maximum power density of 58.1 mW cm−2 at a 260 μWh cm−2 energy density. This work offers a new sight to build transition metal hydroxides-based high performance supercapacitor electrodes with a fast and facile preparation technology.