TY - JOUR
T1 - Redox-Active Macrocycles for Organic Rechargeable Batteries
AU - Kim, Dong Jun
AU - Hermann, Keith R.
AU - Prokofjevs, Aleksandrs
AU - Otley, Michael T.
AU - Pezzato, Cristian
AU - Owczarek, Magdalena
AU - Stoddart, J. Fraser
N1 - Funding Information:
This research was conducted as part of the Joint Center of Excellence in Integrated Nanosystems at King Abdulaziz City for Science and Technology (KACST) and Northwestern University (NU). The authors acknowledge both KACST and NU for their financial support of this research. The Integrated Molecular Structure Education and Research Center (IMSERC) at NU is acknowledged for the use of its facilities.
PY - 2017/5/17
Y1 - 2017/5/17
N2 - 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.
AB - 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.
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U2 - 10.1021/jacs.7b01209
DO - 10.1021/jacs.7b01209
M3 - Article
C2 - 28437104
AN - SCOPUS:85019602876
VL - 139
SP - 6635
EP - 6643
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 19
ER -