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Quino Energy’s water-based organic redox flow batteries are enabled by a number of technological breakthroughs, some of which were first discovered at Harvard University and later licensed by Quino Energy.

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Quinones as a general class of flow battery reactants

Quinones are redox-active molecules that can be easily converted between a reduced hydroquinone form and an oxidized quinone form. Quinones are found in a large number of familiar materials, like Vitamin K1, henna, and a large variety of dyes. Some quinones have high water solubility and high chemical stability, which make them ideal for use as flow battery reactants.

Vitamin K1 phylloquinone
Alizarin 1,2-dihydroxyanthraquinone

Recovery of degraded quinone reactants

Organic molecules such as quinones are cheap and can effectively store electricity, but tend to decompose over time, thereby constraining the useful system lifetime. Careful study of how quinones decompose in flow batteries – via a chemical rather than an electrochemical process – has led to the discovery that the decomposed material can be restored to the original flow battery reactants simply by periodically subjecting the solution of quinone to mild oxidation, either by bubbling air through the battery electrolyte or by simply performing an extra-deep discharge of the flow battery. Unlike lithium-ion batteries, the quinone flow battery is not adversely affected by deep discharge to extremely low states of charge. Other lifetime extension strategies include slightly restricting the depth of discharge of the battery, which has surprising non-linear effects on the overall degradation rate of the quinones.

Decomposition and electrochemical recomposition of flow battery reactants, exemplified by 2,6-dihydroxyanthraquinone (DHAQ)

Innovative zero-waste production of high-performance quinone reactants

Quino Energy has developed a process that converts quinone raw materials – dyestuff chemicals – directly into high-performance, long lifetime quinones using the flow battery system itself as the production reactor. The new quinone produced using this in situ process does not require downstream purification and can be immediately used as a battery reactant with the same flow battery hardware. The process enables a new chemistry to be ramped up rapidly with minimal capital investment while creating zero chemical waste.

Operating without inert gas protection

Atmospheric oxygen tends to oxidize flow battery negolytes, especially in their charged (reduced) state. This causes flow batteries to become unbalanced and fail, unless the electrolyte reservoirs are protected from oxygen, usually by providing a blanket of inert gas such as nitrogen or argon from an external cylinder. Quino Energy has developed a simple technique for rebalancing redox flow batteries and counteracting the effect of atmospheric oxygen while avoiding any long-term water transport issues. This enables Quino’s flow batteries to be operated without any supplemental supply of inert gas, thereby lowering costs and improving system reliability.