2:15 PM - ES02.06.03
Direct Probe of the Nature and Stability of Oxidized Oxygen Environments
Zachary Lebens-Higgins1,Shawn Sallis1,2,Julija Vinckeviciute3,Nicholas Faenza4,Yixuan Li5,Hyeseung Chung5,Nathalie Pereira6,Y. Shirley Meng5,Glenn Amatucci6,Anton Van Der Ven3,Wanli Yang2,Louis Piper1
Binghamton University1,Lawrence Berkeley National Laboratory2,University of California, Santa Barbara3,Exponent4,University of California, San Diego5,Rutgers, The State University of New Jersey6
In the pursuit of high energy density Li-ion battery cathodes, Li-rich systems have demonstrated high reversible capacities that are considered accessible through oxygen redox. Investigation into the oxygen redox mechanism and identification of attractive oxygen redox candidates has driven increased utilization of x-ray spectroscopy techniques that directly probe the oxygen environment. In particular, resonant inelastic x-ray scattering (RIXS) at the O K-edge has emerged as a prime technique to provide sensitivity to the oxygen chemical environment. Sharp RIXS features have been observed in a range of transition metal (TM) 3d systems, including Li-rich NMC , Na2/3[Mg0.28Mn0.72]O2 , and Li1.9Mn0.95O2.05F0.95 , that are considered signatures of oxidized oxygen. Yet, even for the model Li-rich NMC systems, uncertainty in the interpretation of these RIXS features remains as well as questions on the local environment and long-term stability of oxidized oxygen states.
Here, we focus on the stability of Li[Li0.144Ni0.136Mn0.544Co0.136]O2, a model LR-NMC system, at high degrees of delithiation under the x-ray exposure conditions needed to conduct RIXS measurements. Combining sXAS and RIXS, our studies demonstrate the sensitivity of surface transition metal and bulk oxygen states to aggressive x-ray beam exposure in LR-NMC systems. In addition to the surface photoreduction of transition metals, we find a strong loss of inherent oxidized oxygen states with x-ray exposure. Our studies demonstrate the utilization of RIXS for the identification of oxidized oxygen states, while providing new insight into the nature of oxidized oxygen environments.
This work was supported as part of NECCES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012583
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