Journal
SMALL STRUCTURES
Volume -, Issue -, Pages -Publisher
WILEY
DOI: 10.1002/sstr.202200343
Keywords
cathode materials; cation-disordered rocksalts; lithium-ion batteries; oxygen vacancies
Funding
- Umicore Specialty Oxides and Chemicals
- Vehicle Technologies Office, under the Advanced Battery Materials Research Program of the U.S. Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy [DE-AC02-05CH11231, DE-AC02-06CH11357]
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
- US DOE Office of Science User Facility [DE-AC02-05CH11231]
- Department of Energy's Office of Energy Efficiency and Renewable Energy
- Extreme Science and Engineering Discovery Environment (XSEDE) - National Science Foundation [ACI1053575]
- National Energy Research Scientific Computing Center (NERSC)
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Substituting the labile oxygen with a vacancy in cation-disordered Li-rich rocksalt materials is an effective strategy to inhibit oxygen oxidation, leading to improved capacity and voltage retention in lithium-ion batteries.
Li-rich rocksalt oxides are promising cathode materials for lithium-ion batteries due to their large capacity and energy density, and their ability to use earth-abundant elements. The excess Li in the rocksalt, needed to achieve good Li transport, reduces the theoretical transition metal redox capacity and introduces a labile oxygen state, both of which lead to increased oxygen oxidation and concomitant capacity loss with cycling. Herein, it is demonstrated that substituting the labile oxygen in Li-rich cation-disordered rocksalt materials with a vacancy is an effective strategy to inhibit oxygen oxidation. It is found that the oxygen vacancy in cation-disordered lithium manganese oxide favors high Li coordination thereby reducing the concentration of unhybridized oxygen states, while increasing the theoretical Mn capacity. It is shown that in the vacancy-containing compound, synthesized by ball milling, the Mn valence is lowered to less than +3, providing access to more than 300 mAh g(-1) capacity from the Mn2+/Mn4+ redox reservoir. The increased transition metal redox and decreased O oxidation are found to improve the capacity and voltage retention, indicating that oxygen vacancy creation to remove the most vulnerable oxygen ions and reduce transition metal valence provides a new opportunity for the design of high-performance Li-rich rocksalt cathodes.
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