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Scientists have developed a high-performance aqueous organic flow battery

the team of Professor Liu tianpiao of Utah State University in the United States recently designed and developed a new aqueous organic flow battery. This work used a simple and efficient synthesis method to obtain high-performance organic molecular liquid flow battery materials, which further clarified the practical prospect of organic liquid flow battery. This achievement was recently published in the Journal of the American Chemical Society

more than 90% of the energy in people's daily life comes from fossil energy, such as oil, coal and natural gas. However, fossil energy reserves are limited, and a large amount of carbon dioxide and other harmful gases released after mining and combustion cause environmental problems. If renewable energy, such as solar energy and wind energy, is used as much as possible, it can not only achieve the effect of environmental protection, but also bring huge economic benefits

however, the energy intensity of solar and wind energy is unstable. In order to convert unstable renewable energy into stable and usable energy, energy storage is very important. Electrochemical energy storage is an effective way of energy storage, which is respected by governments, academia and industry all over the world. Among various electrochemical energy storage strategies, compared with static batteries, liquid flow batteries have several special technical advantages, which are most suitable for large-scale (MW/MWh) electrochemical energy storage (such as relatively independent energy and power control), high current and high power operation (fast response), high safety performance (not easy to burn and explode), etc

however, the traditional flow battery technology, including vanadium flow battery and zinc bromine flow battery, also has some technical defects, such as self discharge caused by the shuttle effect and low coulomb efficiency due to the penetration of active substances between electrodes; Corrosive electrolyte is not environmental friendly and the resulting safety hazards. The cost of vanadium flow battery is about $450 per kilowatt hour, and the universal price of electrochemical energy storage recommended by the U.S. Department of energy is less than $150 per kilowatt hour, which means the need to develop high-performance, economical and applicable new flow battery technology

in order to overcome the defects of traditional liquid flow batteries, a hot research direction is to use electrochemically active organic molecules to replace traditional non electromechanical active substances in liquid flow batteries. Electrochemically active organic molecules have been widely used in other fields, and many mature organic molecules can be used in liquid flow batteries. Organic molecules are easy to prepare, can be produced on a large scale and at low cost, and have strong plasticity. They can be synthesized and modified to design required functions, such as high potential, high solubility and high compatibility with battery separators

in this new study, the aqueous phase organic liquid flow battery developed by Liu Tianbiao's team uses water-soluble ferrocene as the active material of the positive electrolyte and methyl viologen as the active material of the negative electrolyte, so it is called ferrocene/methyl viologen liquid flow battery. This work is an extension of the previous work of Liu Tianbiao's Methyl Violet semen flow battery

ferrocene is a very stable electrochemically active molecule without any water solubility. The focus of this work is the highly water-soluble amino modified ferrocene developed by molecular design, which can reach the water solubility of 4m, and the solubility of the electrolyte supported by 2m sodium chloride can also reach 3M, with the corresponding theoretical capacitance of 107.2ah/l and 80.4ah/l respectively. This kind of amino ferrocene is very easy to synthesize. The scale of laboratory synthesis is 100 grams, and the yield is more than 95%

Liu Tianbiao said, "the main prospect of this achievement is large-scale energy storage and household energy storage applications. Now the popularity of solar energy and wind energy is getting faster and faster. With the installation of solar panels on the roofs of many community residents, efficient and economical electrochemical energy storage methods are particularly important."

it is necessary to point out that for liquid flow batteries, active substances need simple and high-yield synthesis to reduce costs and adapt to large-scale applications. When paired with high capacitance methyl viologen, the voltage of ferrocene/methyl viologen sperm flow battery is 1.05v, and the theoretical energy density can reach 45.5wh/l, which is higher than that of vanadium liquid flow battery. Ferrocene/methyl violet sperm flow battery uses neutral and environmental friendly sodium chloride to support electrolyte and cheap anion exchange membrane. Ferrocene/methyl violet semen current is the first company to provide a multi-directional polyurethane raw material solution for the insulation and utilization of polyurethane pipes. The pool has been tested for 700 times at a current density of 60ma/cm2 for a long time, with an energy efficiency of about 61%, a capacitance of more than 91%, and a capacitance retention rate of 99.99% per cycle. The test current density can reach 100ma/cm2, and the output power can reach 120mw/cm2

Liu tianpiao said, "the comprehensive performance of this new aqueous phase organic flow battery is the best among the organic flow batteries reported so far, and the estimated cost of this technology is $160 per kWh, which has a good market application prospect." At the same time, Liu Tianbiao pointed out that this work also shows that users will encounter problems that they cannot solve in the process of using and changing the experimental machine, and there are many places that need to be improved, such as finding the reason for the slow decline of capacitance in many factories and construction sites, increasing the cycle type of battery to thousands of times, and there have been some new breakthroughs at present

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