Hierarchical nickel oxide nanoparticles grown on cobalt oxide micro-bricks as battery-type electrode for high-performance hybrid supercapacitors

The battery-type electrode materials with high energy density, long cycle life, and high-rate capability remains a key challenge for next-generation supercapacitors. Conventional transition-metal oxides often suffer from sluggish ion diffusion, poor electrical conductivity, and structural degradation during prolonged cycling, which severely limit their practical performance. Herein, hierarchical NiO 2 /Co 3 O 4 based heterostructures were prepared and systematically addressed the limitations by decoration of NiO 2 on Co 3 O 4 microbricks via synergistic effect of both materials’ electrochemical features. Among the studied electrodes, the NiO 2 /Co 3 O 4 (NCO) heterostructure delivered a high specific capacitance of 278 F g −1 at 1 A g −1 NCO2 and NCO4. Furthermore, the hybrid supercapacitor of NCO demonstrated a specific capacitance of 83 F g −1 , a high energy density of 33 W h kg −1 , and a power density of 8484 W kg −1 . Notably, the device retains 100 % capacitance over 10,000 cycles with 98 % coulombic efficiency. This study underscores that maintaining hierarchical growth of NiO 2 on Co 3 O 4 microbricks and interfacial integrity is highly crucial than phase evolution, offering an effective strategy for designing durable, high-performance supercapacitor electrodes.