Amorphous Thin-Walled Carbon Nanotubes Modified by Simple Oxidation for Zinc-Ion Hybrid Supercapacitors
Siqi Yan, Yakun Tang, Lang Liu, Yang Gao, Yue Zhang, Chensong Yang
Abstract
Carbon nanotubes (CNTs) with superior one-dimensional dynamic properties are good cathode materials for zinc-ion hybrid supercapacitors (ZHSs). Meanwhile, surface oxidation is a productive strategy to boost electrochemical properties of CNTs. Compared with the conventional modification by the mixed strong acid (H 2 SO 4 /HNO 3 ), herein, a strategy is proposed to modify the thin-walled carbon nanotubes (TCNTs) through the oxidation of H 2 O 2 . The abundant −OH of TCNTs-H 2 O 2 can enhance the hydrophilicity of TCNTs and the adsorption ability of Zn 2+ . Moreover, the electrochemical performance of ZHSs is obviously improved due to the synergistic effect between the bilayer capacitance of TCNTs and the pseudocapacitance of oxygen functional groups. Consequently, the assembled ZHSs exhibit excellent energy densities (80 Wh kg –1 at 80 W kg –1 ) and satisfactory long cycle stability (capacitance retention of 100% at 5 A g –1 over 10,000 cycles). In general, TCNTs-H 2 O 2 is a high-performance, very safe, and environmentally friendly electrode material for ZHSs.