Engineering multiscale hollow core-shell nanostructures via in-situ surface functionalization for advanced electrochemical energy storage applications

The development of sustainable energy storage technologies was critical in addressing the global challenges posed by climate change. Supercapacitors, while offering exceptional power density and cycle stability, suffered from relatively low energy density, limiting their widespread use in large-scale energy storage systems. To overcome this limitation, we designed a novel composite electrode material featuring a core-shell structure. The core derived from well-defined ZIF-67 nanocubes (NCs), was innovatively processed into a hollow structure, which enhanced ion diffusion and increases the overall energy storage capacity by reducing internal resistance. Meanwhile, the shell consisted of 3D hierarchical Ni-Co layered double hydroxides (NiCo-LDH) grown in-situ employing an ambient-temperature method, offering high electrochemical activity and abundant active sites for efficient charge storage. This design significantly enhanced the electrochemical performance by improving ion diffusion, increasing surface area, and providing abundant active sites for charge storage. Notably, in-situ Raman spectroscopy was utilized to trace the dynamic redox processes and structural changes occurring during electrochemical cycling, thereby validating the stability and effectiveness of the charge storage mechanism. The resulting material Co3O4-HNC@NiCo-LDH demonstrated impressive capacitance (1862.4 F g-1 at 2 A g-1), high energy density (76.8 Wh kg-1 at 2 A g-1), and excellent cycling stability (98.38 % after 15,000 cycles at 15 A g-1), offering a promising solution for next-generation supercapacitors.