Design Of Dual Redox Additives Of Electrolyte And Studying Synergistic Effect For High Performance Supercapacitors

For the sake of improvement of energy storage efficiency,supercapacitors attach an important role in recent years.Thereby,in this work,it is mainly focused on how to optimize electrochemical performance of supercapacitors.Firstly,high performance electrode materials were carried out by template carbonization.Secondly,introducing two kinds of redox additives into the electrolyte/electrode improve the electrochemical performance of supercapacitors.Meanwhile,the synergy/cooperation effect deriving from simultaneous/continuous the redox reactions among redox additives have been analyzed by a series of electrochemical tools.Finally,some important factors that can markedly influence supercapacitors' performances were explored through the comparisons of electrochemical datum based on several samples.There are analysis results as follows.1.A dual system of redox additive by incorporating Na2MoO4 and KI into H2SO4 solution has been developed to highly elevate the capacitance of supercapacitors primarily owing to the synergistic effect between them at the superposed redox voltage.Furthermore,the synergistic effect therein is attributed to the formation of complex substance of(MoxIyO4x)n-Cz,which can promote redox reaction of Mon+ and In-at the interface of carbon electrode and electrolyte.On the other hand,many crucial factors mainly including the molar ratio,concentration of redox additive and voltage window strongly determine the final capacitive behaviors.For example,when adding Na2MoO4 and KI into H2SO4 with the same concentration of 0.1 mol L-1 the resultant capacitance has remarkably increased by 17.4 times,compared with the one without any redox additive,at 3 A g-1 in a two-electrode system.What's more,the homologous energy density can reach up to 65.3 Wh kg 1 at the suitable voltage window(0?1 V).Hence,the present synergism of various kinds of redox additives is intriguing and easily extended to other systems,which could highly elevate the capacitive performances of supercapacitors.2.Using thiocarbanilide and Mg(OH)2 powders as carbon precursor and template,respectively,novel 2D carbon nanosheets with large area have been produced.Next,based on the cooperative effect,1,4-dihydroxyanthraquinone(DQ)and hydroquinone(HQ)regarded as efficient dual redox additives have been incorporated into the electrode carbon material and H2SO4 electrolyte,respectively,to largely elevate the capacitive performance of supercapacitors.More importantly,the cooperative effect results from the redox processes of DQ and HQ consecutively occurring in the electrode carbon material and aqueous H2SO4 electrolyte,respectively.Besides,the molar ratio of DQ and HQ exerts a crucial role in the determination of the electrochemical behaviors and eventually the optimum condition is the mass ratio of 1:1 concerning the DQ and porous carbon within solid electrode while retaining the HQ concentration as 20 mmol L-1 in 1 mol L-1 H2SO4 electrolyte.As a result,the maximum specific capacitance is achieved of 239 F g-1 at 3 A g-1,and furthermore the maximum energy density up to 21.1 Wh kg-1 is almost 3.5 times larger than that of the one without introducing any redox additives.