TY - JOUR
T1 - Exploring the Origin of Anionic Redox Activity in Super Li-Rich Iron Oxide-Based High-Energy-Density Cathode Materials
AU - Yao, Zhenpeng
AU - Chan, Maria K.Y.
AU - Wolverton, Chris
N1 - Funding Information:
The authors would like to thank Michael Thackeray, emeritus scientist and former battery group leader at Argonne National Laboratory, who worked with John Goodenough back to the past 90s. Z.Y. and C.W. (DFT calculations, analysis of results, and leadership of project) and M.K.Y.C. (discussion of results and editing of manuscript) were supported as part of the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of the Science, Basic Energy Science, under Contract DE-AC02-06CH11357. The authors gratefully acknowledge the computing resources from the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the DOE under Contract DE-AC02-05CH11231, and Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022/5/24
Y1 - 2022/5/24
N2 - Super alkali-rich materials (alkali:transition metal ratio of ≥2:1), such as Li5FeO4, exhibit the potential to realize anionic redox upon deep delithiation. Li5FeO4 was shown to undergo reversible cycling between Li4FeO3.5 and Li3FeO3.5 with combined cation/anion redox, a remarkable capacity of 189 mAh/g, and no O2 release. However, the impact of phase transformations on the reaction thermodynamics and the correlation between the structural changes and reaction reversibility remain unclear. In this study, we use first-principles calculations to examine the delithiation and (re)lithiation reactions of Li5FeO4. We show that the experimentally observed charge and discharge processes go through non-equilibrium pathways. Upon delithiation, the compound undergoes a phase transformation from Li5FeO4, with tetrahedrally coordinated (Td) Fe ions, to a delithiated disordered rocksalt structure, with octahedral (Oh) Fe ions. Fe-ion migration has an asymmetric kinetic barrier that makes Td → Oh migration facile, whereas the reverse process has a much larger barrier, explaining the difficulties in reaction reversibility. We further elucidate the transition metal and O redox sequences during the charge cycle and identify the complex electrochemistry associated with the dual participation of cationic redox (Fe3+/Fe4+) and anionic redox (O2−/O−/O0). Armed with this knowledge, we conduct high-throughput screening of known alkali-rich transition metal oxides by evaluating their potential to enable reversible anionic redox, with multiple candidates proposed for further experimental trials. Our work provides a useful guide for the further development of super alkali-rich anionic-redox-active electrodes for high-energy-density batteries.
AB - Super alkali-rich materials (alkali:transition metal ratio of ≥2:1), such as Li5FeO4, exhibit the potential to realize anionic redox upon deep delithiation. Li5FeO4 was shown to undergo reversible cycling between Li4FeO3.5 and Li3FeO3.5 with combined cation/anion redox, a remarkable capacity of 189 mAh/g, and no O2 release. However, the impact of phase transformations on the reaction thermodynamics and the correlation between the structural changes and reaction reversibility remain unclear. In this study, we use first-principles calculations to examine the delithiation and (re)lithiation reactions of Li5FeO4. We show that the experimentally observed charge and discharge processes go through non-equilibrium pathways. Upon delithiation, the compound undergoes a phase transformation from Li5FeO4, with tetrahedrally coordinated (Td) Fe ions, to a delithiated disordered rocksalt structure, with octahedral (Oh) Fe ions. Fe-ion migration has an asymmetric kinetic barrier that makes Td → Oh migration facile, whereas the reverse process has a much larger barrier, explaining the difficulties in reaction reversibility. We further elucidate the transition metal and O redox sequences during the charge cycle and identify the complex electrochemistry associated with the dual participation of cationic redox (Fe3+/Fe4+) and anionic redox (O2−/O−/O0). Armed with this knowledge, we conduct high-throughput screening of known alkali-rich transition metal oxides by evaluating their potential to enable reversible anionic redox, with multiple candidates proposed for further experimental trials. Our work provides a useful guide for the further development of super alkali-rich anionic-redox-active electrodes for high-energy-density batteries.
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U2 - 10.1021/acs.chemmater.2c00322
DO - 10.1021/acs.chemmater.2c00322
M3 - Article
AN - SCOPUS:85129952818
SN - 0897-4756
VL - 34
SP - 4536
EP - 4547
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 10
ER -