Ultrathin and Porous NiCo₂O₄ Nanosheet-Based Three-Dimensional Hierarchical Electrode Materials for High-Performance Asymmetric Supercapacitor

It is well known that designing unique morphology and the structure of electrode materials is an effective strategy to achieve high-performance supercapacitors (SC). Herein, the ultrathin and porous NiCo₂O₄ nanosheet-based three-dimensional (3D) hierarchical electrode materials were synthesized via a simple and cost-effective solvothermal method and subsequent annealing process. Since the ultrathin and porous nanosheets could accelerate the transmission of ions and provide numerous active sites, the obtained NiCo₂O₄ nanosheet-based electrode exhibited great electrochemical performance with a high area capacity of 5.38 F/cm² (2690 F/g¹) at a current density of 10 mA/cm² and good rate performance of 41% capacitance retention at 50 mA/cm². Furthermore, the corresponding asymmetry supercapacitor was assembled by using the resulted NiCo₂O₄ nanosheets and active carbon as a positive electrode and a negative electrode, respectively. As expected, the corresponding supercapacitor delivered a superior energy density of 52.6 Wh/kg at a power density of 1.1 kW/kg and extraordinary capacitive retention of 80.9% after 3000 cycles at 20 mA/cm². The high-energy storage performances suggested that the obtained ultrathin and porous NiCo₂O₄ nanosheet-based 3D hierarchical electrode materials could be a prospective candidate in the field of energy storage.