All-carbon cord-yarn supercapacitor:

Flexible solid-state yarn supercapacitors were fabricated using commercial carbon fiber and activated carbon fiber. Two methods of yarn construction were studied. One was twisting carbon fiber and activated carbon fiber together (plied yarn), and the other was wrapping activated carbon fiber on carbon fiber (wrapped yarn). Electrochemical measurements in terms of cyclic voltammetry (CV), galvanostatic charge/discharge (GC) and electrical impedance spectroscopy (EIS) were conducted. The result revealed that the cord-yarn structure performed better than the core-spun yarn structure, by showing a specific length capacitance of 82 mF cm−1 at 2 mVs−1. It also exhibited a high specific length energy density of 20.4 μW h cm−1 at a power density of 60 μW cm−1. There was little capacitance reduction when the cord-yarn supercapacitor was bent or crumpled, showing an excellent mechanical flexibility.