Hierarchical Porous NiCo2O4 Microboxes Constructed by Low‐Dimensional Substructures for Electrochemical Supercapacitor

The design and synthesis of new materials/structures for high‐performance electrochemical capacitors (ECs) is an ongoing challenge. Herein, a hierarchical porous NiCo2O4 microbox superstructure made of low‐dimensional substructures was reported. The as‐prepared NiCo2O4 microboxes are constructed by 2D nanosheets building units, which are futher woven by 0D nanoparticles and 1D nanowires. Such microbox superstructures combine the merits of all material dimensions in electrochemical capacitors, such as high porosity, sufficient active sites, and fast mass and charge transport. Benefiting from the structural advantages, the resultant NiCo2O4 microbox electrode exhibits ultra‐high capacitor performance, i.e., the initial capacitance of 1820 F·g–1 and 96.6 % capacitance retention after 4000 cycles at 5 A·g–1.