One-pot combustion synthesis of micro/nanostructured core@shell Ni@Co3O4 hybrid electrodes for extended operational lifespan of binder-free supercapacitors

초록

Three-dimensional (3D) micro/nanostructured metal oxides are promising electrode materials for highperformance supercapacitors due to their large specific surface area, high electrochemical activity, and favorable charge storage properties. However, conventional fabrication methods for such nanostructures are often hindered by multistep processing, high costs, and limited scalability. Herein, we present a one-step combustion wave (CW)-driven synthesis strategy for directly fabricating 3D Ni@Co3Oa core@shell electrodes with outstanding electrochemical performance. This method enables the in-situ formation of micro/nanostructured Co3Oa on a metallic foam substrate without using polymeric binders or post-processing treatments. The process involves drop-casting a metal oxide precursor and a nitrocellulose-based fuel layer onto a Ni foam scaffold, followed by localized ignition at 300 degrees C under ambient conditions. Upon ignition, a self-sustaining CW propagates rapidly across the coated substrate, triggering a highly exothermic reaction that converts the precursor into a conformal Co3Oa nanostructured shell within 0.2 s. The resulting Ni@Co3Oa electrode exhibit a high specific capacitance of 1548 F g-1 at a scan rate of 1 mV s-1, attributed to the rapid and reversible faradaic redox reactions facilitated by the micro/nanostructured Co3Oa surface. Furthermore, the electrodes demonstrate exceptional cycling stability, retaining nearly 100 % of their initial capacitance after 14,000 charge-discharge cycles at 100 mV s-1. The hierarchical 3D porous structure of the Ni@Co3Oa core@shell architecture provides efficient ion transport pathways, ensuring high-rate capability and prolonged operational durability. This CW-based synthesis strategy represents a scalable, energy-efficient, and cost-effective approach for fabricating metal oxide-based energy storage materials under mild temperature and open-air conditions.

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