NiO-bridged MnCo-hydroxides for flexible high-performance fiber-shaped energy storage device

Flexible fiber-shaped supercapacitors (FFSSs) hold promising prospect to meet the increasingly high requirements of the wearable electronics. However, today it remains a great challenge to construct advanced supercapacitor with high areal capacity and favorable rate capability to achieve superior energy density in facile route is a great challenge. Herein, we directly used the low-cost nickel wire as the fiber substrate to in-situ grow compacted NiO buffer layer capable of strongly grafting the outer MnCo-Layered double hydroxide (MnCo-LDH) with high electrochemical reversibility. Compared to MnCo-LDH directly growing on nickel fiber in the absence of NiO, the NiO@MnCo-LDH exhibited 210% enhancement in areal capacity (165.6 mC cm⁻²/368.1 mF cm⁻² at 0.5 mA cm⁻²) and ultrahigh rate capability (85% retention at 20 mA cm⁻²), as synthesized NiO buffer not only served as “nano glue” to strongly immobilize the active materials on the metal substrate but also positively supplied extra capacitance. Thusly, the assembled hybrid/asymmetric fiber device presented a high energy density of 0.0198 mWh cm⁻² at a power density of 0.38 mW cm⁻² to drive a digital watch, demonstrating its promising potential application in electronic devices. This rational design sheds light on the synthesis of nickel fiber-based supercapacitor with high energy delivery.