Abstract
The capacity of lithium transition-metal (TM) oxide cathodes is directly linked to the magnitude and accessibility of the redox reservoir associated with TM cations and/or oxygen anions, which traditionally decreases with cycling as a result of chemical, structural, or mechanical fatigue. Here, it is shown that a capacity increase over 125% can be achieved upon cycling of high-energy Mn- and F-rich cation-disordered rocksalt oxyfluoride cathodes. This study reveals that in Li1.2Mn0.7Nb0.1O1.8F0.2, repeated Li extraction/reinsertion utilizing Mn3+/Mn4+ redox along with some degree of O-redox participation leads to local structural rearrangements and formation of domains with off-stoichiometry spinel-like features. The effective integration of these local “structure-domains” within the cubic disordered rocksalt framework promotes better Li diffusion and improves material utilization, consequently increased capacity upon cycling. This study provides important new insights into materials design strategies to further exploit the rich compositional and structural space of Mn chemistry for developing sustainable, high-energy cathode materials.
Original language | English |
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Article number | 2200426 |
Journal | Advanced Energy Materials |
Volume | 12 |
Issue number | 27 |
DOIs | |
State | Published - Jul 21 2022 |
Funding
The authors thank Prof. Bryan D. McCloskey and Matthew J. Crafton at UC Berkeley for helping with the DEMS measurements and the related discussions, Drs. Michaelle S. Everett and Jagjit Nanda at Oak Ridge National Laboratory for helping with the Neutron diffraction measurements, and Drs. Dennis Nordlund, Eric Nelson, Matthew Latimer, Ryan Davis, Leah Kelly, and Sami Sainio at Stanford Synchrotron Radiation Lightsource for helping with the XAS measurements. The authors appreciate the helpful discussions with Prof. Gerbrand Ceder at UC Berkeley. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE‐AC02‐76SF00515. The NMR studies use shared facilities of the UCSB MRSEC (NSF DMR #1720256), a member of the Materials Research Facilities Network. The TEM work was conducted at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at PNNL. PNNL is operated by Battelle for the Department of Energy under Contract DE‐AC05‐76RLO1830. The neutron diffraction studies (at NOMAD) used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by ORNL. This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE‐AC02‐05CH11231. The authors thank Prof. Bryan D. McCloskey and Matthew J. Crafton at UC Berkeley for helping with the DEMS measurements and the related discussions, Drs. Michaelle S. Everett and Jagjit Nanda at Oak Ridge National Laboratory for helping with the Neutron diffraction measurements, and Drs. Dennis Nordlund, Eric Nelson, Matthew Latimer, Ryan Davis, Leah Kelly, and Sami Sainio at Stanford Synchrotron Radiation Lightsource for helping with the XAS measurements. The authors appreciate the helpful discussions with Prof. Gerbrand Ceder at UC Berkeley. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The NMR studies use shared facilities of the UCSB MRSEC (NSF DMR #1720256), a member of the Materials Research Facilities Network. The TEM work was conducted at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at PNNL. PNNL is operated by Battelle for the Department of Energy under Contract DE-AC05-76RLO1830. The neutron diffraction studies (at NOMAD) used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by ORNL. This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Keywords
- cation-disordered rocksalts
- lithium-ion battery cathodes
- oxyfluoride cathodes
- oxygen redox
- spinel-like domains