Hydrothermally etching commercial carbon cloth to form a porous structure for flexible zinc-ion hybrid supercapacitors

A novel modification method of hydrothermal treatment in acidic potassium chlorate solution is proposed here to etch directly the commercial carbon cloth (CC) surface to produce a porous structure with oxygen-rich functional groups and a large specific surface area (OCC). Following that, an in-situ polypyrrole coating is deposited on OCC (PPy@OCC) to improve conductivity and electrochemical stability. The assembled zinc-ion hybrid super-capacitors (Zn-HSCs) used the PPy@OCC sample as the cathode and Zn foil as the anode, and they demonstrated excellent electrochemical properties. The device has a capacity retention of 92 % after 10,000 cycles at a current density of 20 mA cm-2 and an area capacity of up to 4.74 mAh cm-2 at a current density of 0.5 mA cm-2. It also has a high surface energy density of 4740 Wh cm-2 and a high peak surface power density of 20.23 mW cm-2. When the Zn foil is replaced as the anode to flexible Zn-HSCs by electrodeposited Zn on CC (Zn@CC), the remarkable volume energy density (27.22 mWh cm-3) and flexibility are demonstrated, implying that the pre-pared PPy@OCC is an ideal electrode for high-performance flexible Zn-HSCs.