One‐Step Synthesis of Co‐Ni‐O‐S Nanohybrid with Amorphous‐Nanocrystalline Interwoven Architecture for High‐Energy‐Density Supercapacitor‐Battery Hybrids

Transition metal sulfur oxides have emerged as promising candidates for advanced energy storage due to their multi-electron redox activity and tunable nanostructures. Among them, Co-Ni-O-S composites are particularly attractive for supercapacitors owing to their high energy storage density. However, conventional synthesis methods often require prolonged processing times (>10 h) or high-temperature treatments (>80 °C), which limit their practical applications. This work addresses these challenges by developing amorphous-nanocrystalline intertwined Co-Ni-O-S nanohybrid nanosheet arrays through a rapid alternating current (AC) electrodeposition method (1 h) under ambient conditions. The unique architecture combines the advantages of amorphous phases (enhanced ion diffusion pathways) and nanocrystalline domains (efficient charge transport), leading to exceptional specific capacitance of 4804 F g⁻¹ (or 959 mAh g^-1, 2402 C g^-1) at 1 A g⁻¹, 82.2% capacitance retention after 5000 cycles (5 A g⁻¹), and a near 100% Coulombic efficiency (CE). The assembled asymmetric supercapacitor achieves an energy density of 199.4 Wh kg⁻¹ at 754 W kg⁻¹, bridging the performance gap between batteries and conventional capacitors.