Synthesis Of Electroactive Organic Conjugated Materials And Their Applications In Aqueous Batteries

The rapid development of socio-economics is inseparable from the effective use of energy and resources.The large-scale consumption of more and more non-renewable fossil energy has made ecological and environmental problems more and more prominent.The need to generate electricity from clean,renewable energy sources such as solar,wind and geothermal is growing rapidly.Due to the disadvantages of regional,unbalanced,and intermittent power generation from these renewable energy sources,there is an urgent need to develop efficient and economical electrochemical energy storage systems to alleviate its impact on grid operation.Aqueous redox flow batteries（ARFBs）have the advantages of excellent scalability,flexibility,and low-cost,making them attractive candidates among various electrochemical energy storage technologies.Unlike conventional batteries with solid-state electrodes,redox-active species used in ARFBs are dissolved in the electrolytes.Their limited solubility results in low energy density of ARFBs.To improve energy density so as to compete with traditional batteries,an aqueous hybrid flow battery（AHFB）system was designed and developed by combining a solid organic anode and an inorganic flowing catholyte.The main research contents are as follows:（1）First,an electroactive conjugated organic molecule with low redox potential,dihydroxyanthraquinone disulfonic acid（DHAQDS）,was synthesized through a direct sulfonation reaction,and its electrochemical properties were studied by electrochemical methods such as cyclic voltammetry（CV）.The electrochemical properties and stability in acidic aqueous systems as well as solubility were measured to explore possible flow battery applications.（2）Secondly,a conjugated organic molecule with high redox potential,tetramethylaminemethylene biphenol（TABP）,was synthesized using a Mannich reaction.The electrochemical properties and stability in aqueous solution,the electrochemical kinetic parameters and solubility were measured.Furthermore,an aqueous all-organic flow battery（AORFB）was constructed by employing DHAQDS as the anolyte and TABP as the catholyte,respectively.The open-circuit voltage（OCV）of the DHAQDS//TABP cell is about 0.84 V,and the discharge capacity at a current density of 150 m A(30 m A cm^-2)is 17.94 m Ah(equivalent to a specific capacity of 1.79 Ah L^-1).The active material utilization was33.5%.During 100 continuous charge-discharge cycles,the capacity retention rate is 99.477%per cycle while the coulombic efficiency is about 98.5%.（3）Next,an electroactive molecule with a conjugated aza structure—hexaazanaphthalene（HATN）and its derivatives were synthesized by Schiff-base condensation reaction.The structure and morphology were characterized by nuclear magnetic resonance（NMR）and electron microscopy.The electrochemical properties and stability of these HATN derivatives in alkaline aqueous systems were investigated.An AHFB with HATN as the solid anode material and potassium ferrocyanide as the flowing catholyte was further constructed.The electrochemical reaction mechanism of HATN and the possible reasons for the capacity decay were explored.After 1500 continuous charge-discharge cycles at 8 A g^-1,the capacity retention rate was 99.977%per cycle while the coulombic efficiency and energy efficiency were 99.7%and 75.5%,respectively.（4）Finally,we synthesized electroactive naphthalene tetraketone（NTO）derivatives by a condensation-to-ring reaction using diphenol derivatives and maleic anhydride derivatives as starting reactants.Its molecular structure and morphology were characterized by NMR,thermogravimetric and electron microscopy.Its electrochemical properties and stability in acidic aqueous solution were studied by electrochemical methods such as cyclic voltammetry.The electrochemical kinetic parameters and electrode performance of tetramethylnaphthalenetetraone（TMNTO）in acidic aqueous solution were further investigated.An aqueous symmetric secondary battery using TMNTO as both anode and cathode was further constructed,and its performance and stability were investigated.