期刊
ACS APPLIED MATERIALS & INTERFACES
卷 12, 期 50, 页码 55865-55875出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c16285
关键词
Li-ion batteries; electrode-electrolyte interface; Ni-rich positive electrodes; NMC; X-ray absorption spectroscopy; depth-dependent redox
资金
- BMW
- Canada Foundation for Innovation (CFI)
- Natural Sciences and Engineering Research Council (NSERC)
- National Research Council (NRC)
- Canadian Institutes of Health Research (CIHR)
- Government of Saskatchewan
- University of Saskatchewan
- US Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, Solar Energy Technology Office BRIDGE Program
- Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]
- National Science Foundation [ACI-1548562]
Layered lithium nickel, manganese, and cobalt oxides (NMC) are among the most promising commercial positive electrodes in the past decades. Understanding the detailed surface and bulk redox processes of Ni-rich NMC can provide useful insights into material design options to boost reversible capacity and cycle life. Both hard X-ray absorption (XAS) of metal K-edges and soft XAS of metal L-edges collected from charged LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) showed that the charge capacity up to removing similar to 0.7 Li/f.u. was accompanied with Ni oxidation in bulk and near the surface (up to 100 nm). Of significance to note is that nickel oxidation is primarily responsible for the charge capacity of NMC622 and 811 up to similar lithium removal (similar to 0.7 Li/f.u.) albeit charged to different potentials, beyond which was followed by Ni reduction near the surface (up to 100 nm) due to oxygen release and electrolyte parasitic reactions. This observation points toward several new strategies to enhance reversible redox capacities of Ni-rich and/or Co-free electrodes for high-energy Li-ion batteries.
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