Redox-Active Macrocycles for Organic Rechargeable Batteries

Abstract

Organic rechargeable batteries, composed of redox-active molecules, are emerging as candidates for the next generation of energy storage materials because of their large specific capacities, cost effectiveness, and the abundance of organic precursors, when compared with conventional lithium-ion batteries. Although redox-active molecules often display multiple redox states, precise control of a molecule's redox potential, leading to a single output voltage in a battery, remains a fundamental challenge in this popular field of research. By combining macrocyclic chemistry with density functional theory calculations (DFT), we have identified a structural motif that more effectively delocalizes electrons during lithiation events in battery operations-namely, through-space electron delocalization in triangular macrocyclic molecules that exhibit a single well-defined voltage profile-compared to the discrete multiple voltage plateaus observed for a homologous macrocyclic dimer and an acyclic derivative of pyromellitic diimide (PMDI). The triangular macrocycle, incorporating three PMDI units in close proximity to one another, exhibits a single output voltage at 2.33 V, compared with two peaks at (i) 2.2 and 1.95-1.60 V for reduction and (ii) 1.60-1.95 and 2.37 V for oxidation of the acyclic PMDI derivative. By investigating the two cyclic derivatives with different conformational dispositions of their PMDI units and the acyclic PMDI derivative, we identified noticeable changes in interactions between the PMDI units in the two cyclic derivatives under reducing conditions, as determined by differential pulse voltammetry, solution-state spectroelectrochemistry, and variable-temperature UV-Vis spectra. The numbers and relative geometries of the PMDI units are found to alter the voltage profile of the active materials significantly during galvanostatic measurements, resulting in a desirable single plateau for the triangular macrocycle. The present investigation reveals that understanding and controlling the relative conformational dispositions of redox-active units in macrocycles are key to achieving high energy density and long cycle-life electrodes for organic rechargeable batteries.

Sustainable Energy Storage: Recent Trends and Developments toward Fully Organic Batteries

“…Rings composed of phenylenediimide and cyclohexyl moieties were likewise studied as active materials. Here, the performance of the cell depends strongly on the extent of the formed rings . In comparison to phenylenediimide, naphthalenediimide (NDI) possesses a larger aromatic system and a lower ring strain within the imide moieties.…”

“…Here, the performance of the cell depends strongly on the extento ft he formed rings. [66] In comparison to phenylenediimide, naphthalenediimide (NDI) possessesalarger aromatic system and al ower ring strain within the imide moieties. Thus, NDIs are usually more stable and more often used as active battery material.…”

An Environmentally Friendly and Flexible Aqueous Zinc Battery Using an Organic Cathode

“…[18][19][20][21][22][23][24] Several cathodes materials,s uch as copper hexacyanoferrate, [20] V 2 O 5 , [21,22] and MnO 2 , [23,24] have been coupled with the zinc anode to form the rechargeable aqueous zinc batteries.I nt hese reports,c athodes still involve toxic and/or environmentally unfriendly elements in their components.V ery recently,o rganic electrode materials have been considered as the low-toxicity and sustainable alternative to conventional inorganic electrode materials. [25][26][27][28][29][30][31][32][33][34][35][36] In theory,the combination of organic cathode and zinc anode in mild electrolyte should be ap romising approach for developing low toxic battery,b ecause some organics show very limited toxicity.However,the academic results on this topic are rarely reported. Only very recently,C hen et al first reported an aqueous zinc battery using aq uinone (C4Q)-cathode,w hich shows ah igh energy density.…”

Recent Advances in the Development of Organic and Organometallic Redox Shuttles for Lithium‐Ion Redox Flow Batteries

“…Moreover, other chemistries have also been developed based on the structures of perylene and naphthalenediimide . In summary, n‐type organic molecules have been investigated widely, resulting in a large variety of compounds that have been tested in the Li‐ion RFB system.…”