Electrochemical and Structural Study of the Layered, 'Li-Excess' Lithium-Ion Battery Electrode Material Li[Li[subscript 1/9]Ni[subscript 1/3]Mn[subscript 5/9]]O[subscript 2]

Journal Article · Tue Sep 15 04:00:00 EDT 2009 · Chem. Mater.

DOI:https://doi.org/10.1021/cm900279u· OSTI ID:1005839

Jiang, Meng; Key, Baris; Meng, Ying S; Grey, Clare P

The overcapacity mechanism and high voltage process of the Li-excess electrode material Li[Li{sub 1/9}Ni{sub 1/3}Mn{sub 5/9}]O{sub 2} are studied by solid-state NMR, X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, combined with galvanostatic and potentiostatic intermittent titration electrochemical measurements. The cycling performance is improved noticeably when the material is cycled between potential windows of 5.3-2.5 V compared to 4.6-2.5 V. Diffraction data show that structural changes occur at high voltages, the solid-state NMR data of the same samples indicating that the high voltage processes above 4.4 V are associated with Li removal from the structure, in addition to electrolyte decomposition. The NMR spectra of the discharged samples show that cation rearrangements in the transition metal layers have occurred. The XAS spectra confirm that the Mn oxidation state remains unchanged at 4+, whereas Ni{sup 2+} is oxidized to Ni{sup 4+} on charging to 4.4 V, returning to Ni{sup 2+} on discharge, independent of the final charge voltage. A significant change of the shape of the Ni edge is observed in the 4.6-5.3 V potential range on charge, which is ascribed to a change in the Ni local environment. No O{sub 2} evolution was detected based on ex situ analysis of the gases evolved in the batteries, the TEM data showing that thick passivating films form on the electrodes. The results suggest that at least some of the oxygen loss from these lithium-excess materials occurs via a mechanism involving electrolyte decomposition.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE
• OSTI ID: 1005839
• Journal Information: Chem. Mater., Journal Name: Chem. Mater. Journal Issue: (13) ; 07, 2009 Vol. 21; ISSN CMATEX; ISSN 0897-4756
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
CATIONS
DIFFRACTION
ELECTRODES
ELECTROLYTES
GASES
NMR SPECTRA
OXYGEN
PERFORMANCE
REMOVAL
SHAPE
SPECTRA
TITRATION
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
VALENCE
X-RAY DIFFRACTION