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Title: Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries

Abstract

We introduce a theoretical design approach aiming at improving energy density of redox flow batteries (RFBs) via the utilization of redox non-innocent ligands capable of stabilizing a metal center in a wide range of oxidation states. Our findings suggest that this promotes the possibility of multiple redox events as well as high open circuit voltages. Specifically, we have proposed two Fe-coordination complexes (I, Fe( Me2Pytacn)(C 2N 3H 2), and II, Fe(H 2pmen)(C 2N 3H 2)) combining two different types of ligands, i.e., catalyst-inspired scaffolds and triazole ring, which were previously shown to promote high and low oxidation states in transition metals, respectively. These complexes exhibit as many as six theoretical redox events in the full range of charge states +4 → -2, several of which reside within the electrochemical window of acetonitrile. Electronic structure calculations show that the Fe center exhibits oxidation states ranging from the very rare Fe 4+ to Fe 1+. Values of the reduction potentials as well as nature of the redox events of both complexes is found to be similar in their high +4 → +1 charge states. In contrast, while exhibiting qualitatively similar redox behavior in the lower 0 → -2 range, some differences inmore » the electronic ground states, delocalization patterns as well as reduction potential values are also observed. The calculated open circuit voltages can reach values of 5.09 and 6.14 V for complexes I and II, respectively, and hold promise to be experimentally accessible within the electrochemical window of acetonitrile expanded by addition of ionic liquids. Finally, the current results obtained for these two complexes are intended to illustrate a more general principle based on the simultaneous utilization of two types of ligands responsible for the stabilization of high and low oxidation states of the metal that can be used to design the next-generation charge carriers capable of supporting multi-electron redox and operating in a broad range of charge states, leading to RFBs with greater energy density.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1490770
Alternate Identifier(s):
OSTI ID: 1494464
Report Number(s):
LA-UR-18-28568
Journal ID: ISSN 2296-424X
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Published Article
Journal Name:
Frontiers in Physics
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2296-424X
Publisher:
Frontiers Research Foundation
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; Energy Sciences; Organic Chemistry

Citation Formats

Popov, Ivan A., Davis, Benjamin L., Mukundan, Rangachary, Batista, Enrique R., and Yang, Ping. Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries. United States: N. p., 2019. Web. doi:10.3389/fphy.2018.00141.
Popov, Ivan A., Davis, Benjamin L., Mukundan, Rangachary, Batista, Enrique R., & Yang, Ping. Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries. United States. doi:10.3389/fphy.2018.00141.
Popov, Ivan A., Davis, Benjamin L., Mukundan, Rangachary, Batista, Enrique R., and Yang, Ping. Mon . "Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries". United States. doi:10.3389/fphy.2018.00141.
@article{osti_1490770,
title = {Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries},
author = {Popov, Ivan A. and Davis, Benjamin L. and Mukundan, Rangachary and Batista, Enrique R. and Yang, Ping},
abstractNote = {We introduce a theoretical design approach aiming at improving energy density of redox flow batteries (RFBs) via the utilization of redox non-innocent ligands capable of stabilizing a metal center in a wide range of oxidation states. Our findings suggest that this promotes the possibility of multiple redox events as well as high open circuit voltages. Specifically, we have proposed two Fe-coordination complexes (I, Fe(Me2Pytacn)(C2N3H2), and II, Fe(H2pmen)(C2N3H2)) combining two different types of ligands, i.e., catalyst-inspired scaffolds and triazole ring, which were previously shown to promote high and low oxidation states in transition metals, respectively. These complexes exhibit as many as six theoretical redox events in the full range of charge states +4 → -2, several of which reside within the electrochemical window of acetonitrile. Electronic structure calculations show that the Fe center exhibits oxidation states ranging from the very rare Fe4+ to Fe1+. Values of the reduction potentials as well as nature of the redox events of both complexes is found to be similar in their high +4 → +1 charge states. In contrast, while exhibiting qualitatively similar redox behavior in the lower 0 → -2 range, some differences in the electronic ground states, delocalization patterns as well as reduction potential values are also observed. The calculated open circuit voltages can reach values of 5.09 and 6.14 V for complexes I and II, respectively, and hold promise to be experimentally accessible within the electrochemical window of acetonitrile expanded by addition of ionic liquids. Finally, the current results obtained for these two complexes are intended to illustrate a more general principle based on the simultaneous utilization of two types of ligands responsible for the stabilization of high and low oxidation states of the metal that can be used to design the next-generation charge carriers capable of supporting multi-electron redox and operating in a broad range of charge states, leading to RFBs with greater energy density.},
doi = {10.3389/fphy.2018.00141},
journal = {Frontiers in Physics},
number = ,
volume = 6,
place = {United States},
year = {2019},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.3389/fphy.2018.00141

Figures / Tables:

FIGURE 1 FIGURE 1: Structures of complex I, Fe(Me2Pytacn)(C2N3H2); and II, Fe(H2pmen)(C2N3H2), where Me2Pytacn=1-(2’-pyridylmethyl)-4,7-dimethyl -1,4,7-triazacyclononane, H2pmen=N,N′-bis(2-pyridylmethyl)ethylenediamine, and C2N3H2 = 1,2,4-triazole.

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.