Study On Aqueous Organic Redox Flow Battery Of Alloxazine Derivatives

Redox flow battery is expected to be an ideal energy storage technology,which can effectively overcome the volatility and intermittent problems of renewable energy such as solar and wind energy.Although the traditional flow battery has been developed earlier,it has been confined by the limited resources,strong transmembrane effect,and inherent physical and electrochemical properties.There has been no breakthrough in research and practical application.Organic flow battery benefits from the rich types and sources of materials,the flexible design of organic active material molecules,and the adjustable performance,which is considered to be a feasible alternative.In this paper,the properties of two kinds of active materials of alloxazine derivatives are investigated,and their performance in aqueous battery is evaluated,which indicates the certain feasibility of these two substances as active materials of organic flow battery.First of all,a set of battery test fixture suitable for this research is designed,which is designed by thin snake-shaped runner plate.And the parts and pipes are connected with interference fit,which is more convenient to operate,disassemble and seal.Then a new kind of highly active material alloxazine 7/8-sulfonic acid（ASA）was synthesized by 3,4-diaminobenzenesulfonic acid and alloxan monohydrate.The ASA molecule exhibits high solubility and excellent electrochemical performance under different p H and electrode conditions.Here we propose a high-performance aqueous organic flow battery system by utilizing ASA and K₄[Fe（CN）₆]as the anolyte and catholyte active species,respectively.The assembled ASA/K₄[Fe（CN）₆]battery delivered a cell voltage of 1.11V and realized a peak power density of 0.03 W/cm²under alkaline conditions.The ASA/K₄[Fe（CN）₆]battery can be stably operated at a current of 250 m A（with a coulomb efficiency and capacity retention of～97.7%,73.2%after 100 cycles,respectively）.Finally,we explore a high-performance aqueous flow battery utilizing an organic redox compound,riboflavin（vitamin B2）,which is also an alloxazine derivative.We dissolve it with the help of nicotinamide.The results show that nicotinamide can effectively increase the solubility of riboflavin and has no adverse effect on the redox process.ASA and K₄[Fe（CN）₆]produce an alkaline battery with excellent redox reversibility exhibiting open-circuit voltage approaching 1.0V and coulombic efficiency and capacity retention exceeding 94.6%and 75%over 400 cycles,respectively.