Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short-lifetimes, and expensive ion-selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane-free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof-of-concept of a membrane-free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L⁻¹, and is able to deliver 90 % of its theoretical capacity while showing excellent long-term performance (coulombic efficiency of 100 % and energy efficiency of 70 %).

中文翻译：

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具有两个不混溶的氧化还原电解质的无膜氧化还原液流电池

灵活和可扩展的储能解决方案对于缓解可再生能源的波动是必不可少的。氧化还原液流电池的主要优点是它们能够将功率和能量分离。但是，它们存在一些局限性，包括性能差，寿命短，离子选择膜价格昂贵以及钒化合物的价格高，毒性和稀缺性。我们报告了一种无膜电池，该电池依赖于氧化还原电解质的不溶混性，并且钒被有机分子替代。我们表明，由一种酸性溶液和一种离子液体组成的双相系统，都包含喹啉类，表现为可逆电池，没有任何膜。这种无膜电池的概念验证具有1.4 V的开路电压和22.5 Wh L的高理论能量密度^-1，并且能够提供其90％的理论容量，同时显示出出色的长期性能（库仑效率为100％，能量效率为70％）。