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Lithium- and manganese-rich (LMR) layered oxides are high-capacity cathode materials that are being considered for electric vehicle (EV) lithium-ion batteries (LIBs). Here, we investigate the electrochemical cycling behavior of cells containing a cobalt-free LMR oxide, 0.3Li2MnO3·0.7LiMn0.5Ni0.5O2, paired with either Li or graphite anodes. Two- and three-electrode cells are cycled under varying conditions to examine the effects of oxide activation, upper cutoff voltage, separator type, and electrolyte composition. Post-cycling characterization of harvested electrodes, with electrochemical, X-ray absorption spectroscopy, and solid-state6Li nuclear magnetic resonance spectroscopy techniques, are used to correlate cell performance changes with redox state evolution in the oxide and Li inventory shifts in the cell. Our results show that capacity fade and impedance rise primarily originate at the graphite anode and LMR cathode, respectively. Notably, while Ni undergoes reversible redox, Mn shows no evidence of bulk redox activity even in highly-aged electrodes: only relithiated LMR electrodes show some reduction of Mn. Graphite electrodes degrade due to particle isolation and SEI growth, exacerbated by Mn dissolution and deposition on graphite anodes. These findings highlight the coupled structural and electrochemical degradation mechanisms in LMR/graphite cells and underscore lithium inventory retention and electrode interfacial stability as critical factors for enhancing long-term performance.
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This content will become publicly available on March 1, 2027
Complex‐Concentrated Anion Doping Enables Ultra‐Stable Lattice Oxygen and Structural Integrity in Lithium‐Rich Layered Oxide Cathodes
ABSTRACT Lithium‐ and manganese‐rich layered oxides (LMR) stand out as next‐generation lithium‐ion cathode chemistries, which harness both transition‐metal and lattice‐oxygen redox processes to deliver exceptional capacity and energy density. However, their full potential is hindered by intrinsic oxygen instability and structural degradation, resulting in pronounced voltage fade and capacity decay. Here, we present a complex‐concentrated anion‐doping paradigm in which multiple anions, F, Br, and S, are incorporated into the oxygen sublattice to enhance oxygen‐redox and structural stability. X‐ray absorption spectroscopy and aberration‐corrected scanning transmission electron microscopy confirm ultra‐stable local oxygen coordination environments during long‐term cycling, with detrimental phase transformations and oxygen‐loss‐induced cavitation dramatically inhibited. Notably, we show that the characteristic LiTM6transition metal (TM) honeycomb ordering is preserved even after electrochemical cycling. Concurrently, this strategy yields an unprecedented volume change of only 0.63% upon charging to 4.8 V vs. Li+/Li, achieving the first zero‐strain LMR cathode. The resulting LMR cathode delivers ultralow voltage fade (1 mV per cycle during the first 100 cycles and becomes negligible in subsequent cycles) and outstanding energy retention (93% after 200 cycles) in a pouch cell configuration. Our complex‐concentrated anion‐doping concept establishes a broadly applicable strategy for resolving chemo‐mechanical failure mechanisms in ceramic intercalation electrodes for next‐generation energy storage.
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- Award ID(s):
- 2011967
- PAR ID:
- 10682596
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 38
- Issue:
- 16
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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