TY - JOUR
T1 - Pressure-Dependent Electrochemical Behavior of Di-Lithium Rhodizonate Cathodes
AU - Madsen, Kenneth E.
AU - Shin, Minjeong
AU - Gewirth, Andrew A.
N1 - Funding Information:
This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Science. The work was carried out, in part, in the Materials Research Laboratory Central Research Facilities, University of Illinois, and, in part, at the Microscopy Suite of the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana–Champaign (UIUC-BI-MS).
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/7/27
Y1 - 2021/7/27
N2 - Herein, we investigate the electrochemical properties of the high-capacity organic cathode material di-lithium rhodizonate (Li2C6O6) under different applied mechanical loads. We demonstrate, through a combination of pressure-dependent voltammetry and electrochemical impedance spectroscopy, that the charge-transfer kinetics at the cathode/electrolyte interface is strongly impacted by the magnitude of the load applied to the cathode. At low pressures, lithium rhodizonate displays untenably high charge-transfer impedances toward lithiation and delithiation. As the load applied to the cathode material is increased, the charge-transfer impedance decreases, reflecting a reduction in the overpotential associated with lithiation and delithiation. Furthermore, pressure-dependent galvanostatic cycling reveals that cells cycled at high pressures exhibit improvements in their overall capacity retention when compared with their low-pressure counterparts. Using a combination of postmortem X-ray diffraction and first-principles calculations, we show that, in the absence of sufficient external load, lithium rhodizonate converts from its redox-active structure to a redox-inactive structure, resulting in the observed rapid capacity fade. As the pressure applied to the electrode is increased, this phase transition is suppressed, resulting in improvements in both long-term stability and electrochemical kinetics.
AB - Herein, we investigate the electrochemical properties of the high-capacity organic cathode material di-lithium rhodizonate (Li2C6O6) under different applied mechanical loads. We demonstrate, through a combination of pressure-dependent voltammetry and electrochemical impedance spectroscopy, that the charge-transfer kinetics at the cathode/electrolyte interface is strongly impacted by the magnitude of the load applied to the cathode. At low pressures, lithium rhodizonate displays untenably high charge-transfer impedances toward lithiation and delithiation. As the load applied to the cathode material is increased, the charge-transfer impedance decreases, reflecting a reduction in the overpotential associated with lithiation and delithiation. Furthermore, pressure-dependent galvanostatic cycling reveals that cells cycled at high pressures exhibit improvements in their overall capacity retention when compared with their low-pressure counterparts. Using a combination of postmortem X-ray diffraction and first-principles calculations, we show that, in the absence of sufficient external load, lithium rhodizonate converts from its redox-active structure to a redox-inactive structure, resulting in the observed rapid capacity fade. As the pressure applied to the electrode is increased, this phase transition is suppressed, resulting in improvements in both long-term stability and electrochemical kinetics.
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U2 - 10.1021/acs.chemmater.1c01523
DO - 10.1021/acs.chemmater.1c01523
M3 - Article
AN - SCOPUS:85111216065
SN - 0897-4756
VL - 33
SP - 5738
EP - 5747
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 14
ER -