The Electrochemical Mechanism Of Polyaniline/Graphene Composites Electrode Material

In recent years,polyaniline/graphene(PANI/graphene)composite electrode materials have been extensively studied and became one of the most popular electrode materials in supercapacitors,because of their high capacitance,long lifetime,and excellent rate performance.However,the functions of PANI and graphene in the composite have not been fully understand.Especially,it is puzzling that the capacitance of PANI/graphene composite electrodes can far exceed the calculated theoretical specific capacitance.Researchers often attribute their ultra-high capacitance performance to the synergistic effect between high-capacity PANI and graphene materials.This reflects the fact that researchers do not really understand the working mechanism of polyaniline/graphene electrode materials.The poor understanding of mechanism also limits the further development of polyaniline/graphene composite electrode materials.In this paper,we systematically study the working mechanism of polyaniline/reduced graphene oxide composite electrode materials in supercapacitors,and for the first time,reveal the contribution of polyaniline electrochemical degradation to energy storage,and elucidate the reasons of high capacitance of such composite materials.In second chapter,we demonstrate that polyaniline will degrade and produce hydroxyl-or amino-terminated aniline oligomers(HAOANIs)during electrochemical testing(≥0.8 V vs.SCE).A calculation indicates that the theoretical specific capacitance of these oligomers can reach up to 1000 F g-1,but the rather low conductivity of HAOANIs will cause a sharp increase in the resistance of PANI,restricting the performance of the electrode.The high electrical conductivity of graphene,however,improves the electrical conductivity of the composites in polyaniline/graphene composites,which maximizes the specific capacity of the HAOANIs.In the third chapter,we tried to design high-capacity electrode materials based on HAOANIs.Finally,based on the results of the last chapter,we design an in-situ activation method to improve the performance of PANI/graphene composite electrode.A PANI/HAOANIs/graphene composite electrode is obtained with high specific capacitance of up to 772 F/g at a current density of 1.05 A/g.After 10,000 cycles,there is still 91.7%of the capacitor retention,far beyond the performance of other similar materials reported in the literature.This work elucidates the working mechanism of PANI/graphene composite electrode materials.The conclusion will change our understanding of the degradation of polyaniline,and guide the design of other PANI-based composite electrode materials.