The high performance of polyaniline-gel network modified electrode in 3-(2,2,6,6-tetramethyl-piperidiynl-l-oxyl)-l-methylylimidazoliumbromide biredox electrolyte used for supercapacitor

摘要

Improving energy density while maintaining power density and cycle stability is the most serious challenge for supercapacitors. The solid active electrode material might possess a higher redox species density compared with its traditional counterpart, however, its electrochemical reaction kinetics is several magnitude orders lower in solids than that in liquids, leading to a deterioration of power density. Thus, a new approach based on 3-TEMPO-1-methylylimidazolium bromide (MIm(+)-TEMPO center dot Br-) biredox electrolyte, and a PANI-gel network modified carbon paper (PNcp) electrode for supercapacitor were developed in this study. The biredox electrolyte possesses a high energy density comparable to solid redox materials and a fast kinetics of liquid redox reaction, while the cross-diffusion of ions leads to a serious voltage drop which presents an inherent self-discharge problem. Fortunately, the PNcp prepared by a millisecond photo-thermal process makes up for this shortcoming. On one hand, its unique PANI-gel network structure protects the biredox electrolyte from cross-diffusion phenomenon, on the other hand, the combination of doping/dedoping process of PANI and redox process of MIm(+)-TEMPO center dot Br- provides an extra effect to prevent the self-discharge and attain a synergetic electrochemical performance. This method explores an avenue to pursue for battery level energy density meanwhile maintains good power density.