Binder-free preparation of bimetallic oxide vertical nanosheet arrays toward high-rate performance and energy density supercapacitors

Fabrication of binder-free electrode materials with vertical nanoarchitecture is the prominent approach to achieve exalted energy storage performance. Herein, we synthesized NiCo2O4 (NCO) zigzag-patterned vertical nanosheet arrays (ZNSAs) directly over the nickel foam substrate by adopting a facile one-step solvothermal method, which is followed by a calcining process. The effect of ethanol and water solvents on the development of ZNSAs was studied by varying their volume concentration. Among the samples, the NCO ZNSA electrode prepared with an equal volume proportion of ethanol and water solvents revealed the highest electrochemical performance with the areal capacity of 146.1 mu Ah/cm(2) at 4 mA/cm(2) due to the well-developed NSAs with hierarchical and open-porous texture. Moreover, the NCO ZNSA electrode exhibited remarkable stability (97.6% retention) after the cycling process of 4000 cycles. A hybrid supercapacitor (HSC) device was also constructed with NCO ZNSAs and activated carbon as the cathode and anode, respectively. At 2 mA/cm(2), the HSC showed a notable areal capacitance of 173.5 mF/cm(2). Furthermore, the HSC exhibited a maximum energy density of 52.7 mu Wh/cm(2) and power density of 10500 mu W/cm(2). With the energy storage capabilities, the HSC demonstrated its practical applicability by glowing light-emitting diodes and powering up a motor fan.

Automated summary

The fabrication of NiCo2O4 zigzag-patterned vertical nanosheet arrays using a one-step solvothermal method resulted in electrodes with high electrochemical performance, especially when prepared with an equal volume proportion of ethanol and water solvents. Furthermore, a hybrid supercapacitor device using these nanosheet arrays demonstrated remarkable energy and power densities, showcasing their practical applicability in powering devices like light-emitting diodes and motor fans.