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

Abstract

The development of sustainable energy storage technologies is critical in addressing the global challenges posed by climate change. Supercapacitors, while offering exceptional power density and cycling stability, suffer 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 increased 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. The ultimately synthesized multi-scale hollow core–shell material, Co₃O₄-HNC@NiCo-LDH, integrated the respective merits of the shell and core materials, while simultaneously addressing issues that arise when these materials exist in isolation. It effectively mitigated problems such as volume expansion and agglomeration that materials might encounter during electrochemical reactions, thereby further enhancing the materials’ performance and service life. 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.