Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session F64: Advances in Li-ion and Li-S Energy Storage
8:00 AM–10:36 AM,
Tuesday, March 5, 2024
Room: 211AB
Sponsoring
Units:
GERA FIAP
Chair: Santidan Biswas, University of Pittsburgh
Abstract: F64.00004 : Understanding the redox sequence of VFe2Ox and the role of dopants (Al, Zn, Zr) in shifting capacity and cycling profiles*
8:36 AM–8:48 AM
Presenter:
Michelle D Johannes
(United States Naval Research Laboratory)
Authors:
Michelle D Johannes
(United States Naval Research Laboratory)
Noam Bernstein
(United States Naval Research Laboratory)
Michael Swift
(Naval Research Laboratory)
Ryan DeBlock
(Naval Research Laboratory)
Jeffrey Long
(Naval Research Laboratory)
Hunter Ford
(Naval Research Laboratory)
Rachel Ashmore
(Naval Research Laboratory)
Debra R Rolison
(Naval Research Laboratory)
We use density functional theory calculations in concert with in-situ and operando X-ray absorption near-edge spectroscopy (XANES) spectra obtained from measurements at the Naval Research Laboratory to uncover the quantum mechanical-level effects that underpin relevant energy storage behaviors of doped and undoped VFe2Ox. Our experimental V K-edge and Fe K-edge spectra indicate reduction of both species during discharge, but cannot distinguish between tetrahedral and octahedral Fe redox sites or fully resolve the valency of each element as a function of state of charge. Using a hybrid form of density functional theory that accounts for the strong correlation present in 3d elements, we show that both V and Fe are indeed reduced, but that only tetrahedral Fe is redox active until fully converted to Fe2+. Furthermore, both octahedral and tetrahedral Fe3+ are high spin configuration, but the 5mB moments in the fully filled majority spin channel at each symmetry site are anti-aligned. This allows for easy exchange of electrons and facilitates conduction. We also calculate XANES spectra based on first principles calculations3 to be compared directly to those measured in the lab. This allows us to understand the effect of Al, Zr, and Zn dopants on the redox sequence and relate these results to site preference and capacity. Our combined experimental and calculational investigation sheds light on how these complex materials store Li ions and points toward future alterations that may further improve their properties.
*ONR Award Number: N0001423WX00604
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