Abstract
Designing Li-ion battery cathodes free of critical raw materials such as Co and Ni has a huge technological and societal impact. Although anion redox-based Li-rich oxide cathodes allow for designing Co- and Ni-free cathode compositions, the Li-rich oxides demonstrated voltage fade, voltage hysteresis, and irreversible oxygen release despite their high capacity. Conversely, anion redox through highly covalent chalcogenides (S/Se) is emerging due to the improved covalency between metal d and ligand p bands. Here, we investigate the tuning of multichalcogen (S/Se) p band and redox-active metal d band in a model Li-rich chalcogen composition, Li1.13Ti0.57Fe0.3S2-ySey (y = 0-1), through in-depth electrochemical, X-ray spectroscopy, and DFT-based electronic structure investigations. Introducing the appropriate amount of Se p band character in anion redox sulfides increases the interlayer distance and metal-ligand covalency without modifying the original crystal structure, promoting significant electrochemical reversibility through mixed anionic (Se2-/Sen-, S2-/Sn-, wherein n < 2) and cationic (Fe2+/Fe3+) redox reactions. We show the detailed Fe, S, and Se redox contributions during Li insertion-extraction through X-ray absorption (XAS) and hard X-ray photoemission spectroscopy (HAXPES) measurements. The orbital tuning approach improves the rate capability for more than 10C charge-discharge rate, exhibiting more than 50% of its original capacity obtained at the C/20 rate. The buffer cation in the lattice (Ti4+) remains electrochemically inactive even after significant Se p band introduction in the sulfide framework. Overall, this work takes advantage of multianion redox chemistry to uncover practically demanding fast charging-discharging characteristics in intercalation cathodes. The obtained knowledge of this design can be extended to other oxide and chalcogen cathodes for high-performance Li-ion batteries.
| Original language | English |
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| Journal | Chemistry of Materials |
| DOIs | |
| State | Accepted/In press - 2024 |
Funding
This work was primarily supported by the National Science Foundation under grant number 2127519. This research used resources of the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract DE-SC0012704. The HAXPES and NEXAFS measurements were performed at the National Institute of Standards and Technology (NIST) beamline SST-2 in the NSLS-II. This research also used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract DE-SC0012704. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract DE-AC02-06CH11357 and the Canadian Light Source and its funding partners. The theoretical analysis in this work was supported by a User Project at The Molecular Foundry and its computing resources, managed by the High-Performance Computing Services Group at Lawrence Berkeley National Laboratory (LBNL). This research also used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at LBNL. The LBNL facilities employed in this work were supported by the Director, Office of Science, Office of Basic Energy Sciences of the United States Department of Energy under Contract DE-AC02-05CH11231. This work used resources of the Lumigen Instrument Center at Wayne State University for the use of XRD (NSF: MRI 1427926) facility.