Although high operating voltages have been achieved in asymmetric supercapacitors, remarkably capacitive electrode materials with simple and cost-effective synthesis method is highly necessary to fabricate high-energy-density supercapacitors.

Recently, Prof. YAO Yagang's group at Suzhou Institute of Nano-tech and Nano-bionics of Chinese Academy of Sciences reported a simple and cost-effective method to directly grow three-dimensionally well-aligned Zinc-Nickel-Cobalt oxide (ZNCO)@Ni(OH)₂ nanowire arrays (NWAs) on carbon nanotube fiber (CNTF) with ultrahigh specific capacitance of 2847.5 F/cm³ (10.678 F/cm²), which is approximate five times higher than that of ZNCO NWAs/CNTF electrode (2.10 F/cm²) and four times of Ni(OH)₂/CNTF electrode (2.55 F/cm²) at a current density of 1 mA/cm².

Benefiting from outstanding electrochemical performance of (ZNCO)@Ni(OH)₂, a prototype coaxial fiber-shaped asymmetric supercapacitors (CFASCs) with a maximum operating voltage of 1.6 V was successfully fabricated by adopting ZCNO@Ni(OH)₂ NWAs/CNTF as the core electrode and thin carbon layer coated vanadium nitride (VN@C) NWAs on carbon nanotube strip as the outer electrode. This CFASC device had a high specific capacitance of 94.7 F/cm³ (573.8 mF/cm²) and an exceptional energy density of 33.66 mWh/cm³ (204.02 μWh/cm²).

Importantly, this CFASC was also applied to power an integrated fiber-shaped ZnO-based photodetector. This integrated wearable device was highly sensitive to UV light.

The successful construction of ultrahigh-capacity ZCNO@Ni(OH)₂ core-shell heterostructures opens the door to design new electrode materials for next-generation wearable supercapacitors. This study was published in Nano Letters.