Naphthalene diimides (NDI) in highly stable pH-neutral aqueous organic redox flow batteries

In the pursuit of environmentally friendly energy storage, aqueous organic redox flow batteries (AORFBs) that use naphthalene diimide hold promise for successful application. present article, two different diimides (NDI) are studied as negative electrolyte materials pH-neutral organic/organometallic batteries. The molecules, one core-unsubstituted NDI (2H-NDI) and core-dimethylamino substituted (2DMA-NDI) coupled with a solubilized ferrocene (BTMAP-Fc) at concentration 50 mM in phosphate buffered potassium chloride. High efficiencies coulombic were obtained both batteries, but gradual capacity fade was observed while cycling. However, when changing cation supporting from to ammonium, similar obtained, undetectable losses over 320 cycles. Finally, 2H-NDI BTMAP-Fc 500 tested ammonium-based electrolyte, obtaining high efficiency, efficiency cycling stability decreased compared same system lower concentration. It is concluded loss activity mainly due formation electrochemically inactive compounds great importance outcome. Important design strategies AORFB molecules include using salts prevent self-association introducing sterically hindering substituents structures.