Verdazyl free radical compounds are promising candidates for symmetrical all-organic redox flow batteries (RFBs) due to their redox stability, the ease with which their chemical structure can be varied, and...
Host‐guest interactions are an attractive approach to design redox electrolytes, enabling to precisely tune the key properties for redox flow batteries such as half‐cell redox potential, solubility, and stability. Herein we report a host‐guest complex of highly water soluble (2‐hydroxypropyl)‐β‐cyclodextrin with 1‐decyl‐1′‐ethyl‐4,4′‐bipyridinium dibromide as anolyte in a new aqueous organic redox flow battery (AORFB). The supramolecular anolyte ensured the total RFB voltage increase of ≈9 % up to 0.97 V and provided a stable capacity delivery for more than 500 cycles with a capacity fade rate of 0.037 %/cycle (2.84 %/day) at high Coulombic (>99.5 %) and energy (>62 %) efficiencies. The results highlight host‐guest interactions as promising strategy towards more effective storage of renewable energy within AORFBs.
Along with a primary
modification of redox active materials, an
additional introduction of secondary noncovalent interactions can
synergistically enhance bulk properties of electrolytes for redox
flow batteries. Herein, we highlight the host–guest complex
formation between tailored viologens and highly water soluble (2-hydroxypropyl)-β-cyclodextrin
as a key electrolyte interaction to modulate relevant electrochemical
properties of aqueous redox flow batteries (AORFBs). The cyclodextrin-modified AORFB anolytes demonstrated
a complex interrelation of molecular structure and inherent binding
activity as well as bulk electrochemical stability of the anolyte.
The screening of different combinations of viologen substituents in
the presence of cyclodextrin enabled an electrochemically stable AORFB
performance for more than 500 cycles with a temporary capacity fade
rate of 0.26%/day at high energy (>70%) and Coulombic (>99.7%)
efficiencies.
A selective interplay of supporting electrolytes and engineered redox
active materials is a promising strategy for enhanced energy characteristics
of AORFB electrolytes.
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