Supercapacitors can store a lot more energy than other capacitors and deliver it much faster than a rechargeable battery. Flexible supercapacitors could be particularly useful for flexible and wearable electronics. As materials for such devices, metal oxides can provide high energy densities, while carbon nanotubes (CNTs) are highly flexible.
Qiufan Wang, Daohong Zhang, South-Central University for Nationalities, Wuhan, China, Menghe Miao, CSIRO Manufacturing, Waurn Ponds, Australia, and colleagues have combined both those materials to produce flexible linear supercapacitors with high energy densities. The team first created a two-ply yarn by twisting a copper nanowire around a fiber made from CNTs. Nanostructured NiCo2O4 was then deposited on the yarn using a hydrothermal method to give finished electrodes (pictured). The metal oxide’s nanostructure depends on the reaction time. The electrodes were coated with a poly(vinyl alcohol) (PVA)/KOH gel electrolyte and two electrodes were combined to form a supercapacitor.
The developed supercapacitor has an energy density of 35.76 mWh cm–2 and a power density of 0.154 mW cm–2. The device is flexible and can be woven into fabric without losing its storage capacity. The material’s capacitance remains at 89 % after 5000 charge/discharge cycles. The device could, for example, be used to power light-emitting diodes (LEDs).
- Fabrication of Supercapacitors from NiCo2O4 Nanowire/Carbon-Nanotube Yarn for Ultraviolet Photodetectors and Portable Electronics,
Qiufan Wang, Daohong Zhang, Yunlong Wu, Ting Li, Aiqing Zhang, Menghe Miao,
Energy Technol. 2017.