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Title: Observation of Electron-Beam-Induced Phase Evolution Mimicking the Effect of the Charge–Discharge Cycle in Li-Rich Layered Cathode Materials Used for Li Ion Batteries

Capacity loss, and voltage decrease upon electrochemical charge-discharge cycling observed in lithium-rich layered cathode oxides (Li[Li xMn yTM 1-x-y]O 2, TM = Ni, Co or Fe) have recently been attributed to the formation of a surface reconstructed layer (SRL) that evolves from a thin (<2 nm), defect spinel layer upon the first charge, to a relatively thick (~5nm), spinel or rock-salt layer upon continuous charge-discharge cycling. Here we report observations of a SRL and structural evolution of the SRL on the Li[Li 0.2Ni 0.2Mn 0.6]O 2 (LNMO) particles, which are identical to those reported due to the charge-discharge cycle but are a result of electron-beam irradiation during scanning transmission electron microscopy (STEM) imaging. Sensitivity of the lithium-rich layered oxides to high-energy electrons leads to the formation of thin, defect spinel layer on surfaces of the particles when exposed to a 200kV electron beam for as little as 30 seconds under normal high-resolution STEM imaging conditions. Further electron irradiation produces a thicker layer of the spinel phase, ultimately producing a rock-salt layer at a higher electron exposure. Atomic-scale chemical mapping by electron dispersive X-ray spectroscopy in STEM indicates the electron-beam-induced SRL formation on LNMO is accomplished by migration of the transitionmore » metal ions to the Li sites without breaking down the lattice. The observation through this study provides an insight for understanding the mechanism of forming the SRL and also possibly a mean to study structural evolution in the Li-rich layered oxides without involving the electrochemistry.« less
 [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [2]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environmental Directorate
Publication Date:
Report Number(s):
Journal ID: ISSN 0897-4756; 547707
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 27; Journal Issue: 4; Journal ID: ISSN 0897-4756
American Chemical Society (ACS)
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
OSTI Identifier: