CHEMICAL SCIENCE

Based on the active molecule stabilization mechanism, the kilowatt-class organic flow battery stack was developed


The cover image was produced by the Science Visualization Center of China Science Daily

Recently, the team of researcher Li Xianxiang and researcher Zhang Changkun of the Energy Storage Technology Research Department (DNL17) of Dalian Institute of Chemical Physics, Chinese Academy of Sciences has made new progress in the research of organic flow batteries in water systems.

The results were published in Energy & Environmental Science under the title “Insight into Air-stable Methylene Blue Catholyte towards kW-scale Practical Aqueous Organic Flow Batteries.”

The first author of this work is Zhang Yonghui, a graduate student jointly trained by Dalian Institute of Chemicals.

Recently, the team of researcher Li Xianxang and researcher Zhang Changkun of the Energy Storage Technology Research Department of Dalian Chemical Institute (DNL17) has made new progress in the research of organic flow batteries in water systems. The team used electrochemical-in situ/ex situ NMR and electron spin resonance methods to reveal the stabilization mechanism of Methylene Blue (MB) molecules in the actual working conditions of the battery. It is found that the stability of intermediate radicals and reduced states plays a crucial role in the reversibility and air durability of redox reactions of MB molecules. Based on such molecules, the team developed a kilowatt-level aqueous organic flow battery stack, which provides an important reference for the practical application of aqueous organic flow batteries.

Flow batteries (FBs) have the advantages of high safety and high efficiency, and have received widespread attention in the field of large-scale energy storage. Aqueous organic flow batteries have attracted more and more attention from researchers because their active electric pairs are small organic molecules synthesized by organic synthesis or extracted from nature, which have the advantages of strong structural tunability and environmental friendliness. However, at present, the vast majority of organic molecules are easily oxidized in the air, resulting in irreversible attenuation of capacity. Therefore, the development of air-stable high-performance organic active molecular materials is of great significance to the research of organic flow batteries.

In this work, the team optimized the electrolyte components by studying the interaction between different components in the electrolyte, which greatly improved the battery capacity. Through electrochemical-in situ NMR technology, the team found that MB molecules undergo a centering reaction to form free radical states when the battery is running. The results of electron spin resonance technology and theoretical calculation show that the stability of free radical state and reduced state in air is an important reason for the high reversibility and structural stability of the electrochemical reaction of this molecule. In order to further verify the feasibility of the application of MB molecules in organic flow batteries, the team assembled 10 1000cm2 organic flow battery stacks, the instantaneous discharge power of the stacks exceeded 1kW, and operated continuously for 32 days with almost no attenuation of capacity. In addition, the team also carried out an accelerated life attenuation test on the MB electrolyte at a high temperature of 70 °C, and analyzed its possible attenuation mechanism. This study not only explains the oxidation resistance mechanism of organic active molecules, but also provides an important reference for the design of molecules. Moreover, the developed kilowatt-class stack is expected to provide a good reference for the practical application of aqueous organic flow batteries.

The above work has been supported by the National Natural Science Foundation of China, the International Cooperation Project of the Chinese Academy of Sciences, the National Key Research and Development Program and other projects. (Source: Science Network)

Related paper information:https://doi.org/10.1039/D2EE03051A



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