Synthesis of self-templated urchin-like Ni₂Co(CO₃)₂(OH)₂ hollow microspheres for high-performance hybrid supercapacitor electrodes

Developing novel nanostructures is always the most decisive aspect for high-performance supercapacitor electrodes. Thus, a facile one-step and self-templated method is successfully developed for the fabrication of urchin-like Ni₂Co(CO₃)₂(OH)₂ hollow microspheres (NiCoHSs) as a high-performance hybrid supercapacitor electrodes. The synthesis conditions are carefully adjusted and the mechanisms of morphology transformation are clearly illustrated. The favorable morphology with a large specific surface area, suitable pore sizes, and good conductivity endows a high specific capacity (890.8 C g⁻¹ at 0.5 A g⁻¹) and excellent rate retention (700.8 C g⁻¹ at 50 A g⁻¹), and high stability (87.5% over 5000 cycles), which outperforms most reported electrodes based on nickel-cobalt oxides/hydroxides. Contributed by the uniquely engineered electrodes, a high-performance hybrid supercapacitor (HCS) is assembled, which exhibited a high specific capacity of 256.9 C g⁻¹ (160.5 F g⁻¹) at 0.5 A g⁻¹ with an operating voltage of 1.6 V and an outstanding energy density of 57.1 W h kg⁻¹ at a power density of 400.0 W kg⁻¹. This work offers a facile self-templated method to fabricate bimetal Transition-metal oxides (TMOs) electrodes for hybrid supercapacitors.