The Application Of Redox-Active Gel Polymer Electrolyte And Eggshell Membrane In Supercapacitor

Supercapacitors are considered as the most promising candidate for energystorage due to its high power and energy performance. Owing to this, supercapacitorshave aroused a widely research and attracted a considerable development. Theobjective of this paper was to try to solve the problems in stability and practicalapplication of supercapacitors. Accoding the research progress at home and abroad,the following subjects were studied deeply. Firstly, High-property and novel redox-active gel electrolytes （PVA-KOH-KI and PVA-H₂SO₄-PB） were prepared basing onthe matrix of polyvinyl alcohol, KOH and KI or polyvinyl alcohol, H₂SO₄and p-Benzenediol. Subsequently, the quasi-solid-state supercapacitors employing the newelectrolytes were assembled and researched, respectively. Secondly, a separator wasprepared based on natural and flexible eggshell membrane （ESM） for supercapacitorapplication. The paper mainly obtained the following important conclusions.The optimized conditions for preparing PVA-KOH-KI redox-active gelelectrolyte by sol-gel method were obtained finally after the preparing procedureswere studied systemly and deeply. The optimized is to use0.6g KI as additive.Subsequently, the ion conductivity of PVA-KOH-KI redox-active gel electrolyte is12.73mS cm^–1. And the specific capacitance of the quasi-solid-state supercapacitor is236.90F g^–1, increasing by74.28%compared to the PVA-KOH system at the samecurrent density. The energy density and power density of the supercapacitor reach7.80Wh kg^–1and779.20W kg^–1, respectively. In addition, the supercapacitorexhibits excellent cycle-life stability and low self-discharge performance.After optimizing the condition for preparing PVA-H₂SO₄-PB redox-active gelelectrolyte through the sol-gel method, the mass of additive PB is determined to0.2g.The ion conductivity of PVA-H₂SO₄-PB redox-mediated gel polymer electrolyte is ashigh as to34.8mS cm^–1. It is found that the supercapacitor exhibits large specificcapacitance reaches to474.29F g^–1, increasing by3folds compared to the undopinggel electrolyte system. Besides, the energy density and power density of the supercapacitor also are enhanced largely, which are14.30Wh kg^–1and1949.58Wkg^–1, repectively. Furthermore, it can be inferred that the supercapacitor exhibitesoutstanding cyclic atability from the result of high-capacitance retention （90.77%）after3000cycles.In the new redox-active electrolyte system, the supercapacitor can be regarded asa novel hydrid supercapacitor application that combines two energy-storage processes:the double-layer formation （double-layer capacitance） characteristic of carbon-basedsupercapacitor and the faradaic reactions （pseudocapacitance） characteristic ofbatteries at the electrode|electrolyte interface. So, the properties of supercapacitors areimproved enormously.The ESM was prepared by sol-peel off method. The experimential results showsthat the ESM is consisted of hierarchically ordered macroporous fiber network.Besides, ESM exhibits a high decomposition temperature （>220oC）, enoughmechanical strength （σmax=6.59±0.48MPa, εmax=6.98±0.31%）, and low wateruptake and swelling property （Dw=10%, Ds=8%）. As expected, the supercapacitorwith ESM separator exhibits outstanding electrochemical performances, such asequivalent series resistance （ESR,0.01Ω）, quick quick charge-discharge ability（dielectric relaxation time is4.76S）, and good cyclic stability （92%retention after10,000cycles）.