Synthesis Structure Property Relations in Layered, Li-excess Oxides Electrode Materials Li[Li1/3-2x/3NixMn2/3-x/3]O2 (x=1/3, 1/4 and 1/5)

Journal Article · Fri Jan 01 00:00:00 EST 2010 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.3473830· OSTI ID:1024656

Fell, Christopher ^[1]; Carroll, Kyler ^[2]; Chi, Miaofang ^[3]; Meng, Ying Shirley ^[1]

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1. University of Florida, Gainesville
2. Virginia Commonwealth University, Richland
3. ORNL

Relations between synthesis conditions, detailed crystal structures, and electrochemical properties of the Li-excess layered oxides Li[Ni{sub x}Li{sub 1/3-2x/3}Mn{sub 2/3-x/3}]O{sub 2}(0 < x < 1/2) are studied by X-ray diffraction, scanning electron microscopy (EELS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron energy-loss spectrometry, combined with electrochemical property measurements including potentiostatic intermittent titration technique (PITT). Optimal synthesis conditions are obtained for stoichiometric samples sintered at 1000 C in air followed by furnace cooling. The materials exhibit capacities of {approx}250, 230, and 200 mAh/g within a voltage range of 2-4.8 V on discharge for x = 1/5, 1/4 and 1/3, respectively. Diffraction data of electrochemically cycled electrode materials show an expanded c/a lattice ratio and changing Li/Ni interlayer mixing indicating peculiar cation migration in the structures. High resolution TEM images and XPS spectra show obvious differences in the surface characteristics of the samples synthesized with stoichiometric and excess amount of LiOH, suggesting that surface characteristics is one of the contributing factors to the difference in electrochemical properties. Our results suggest that the first cycle irreversible capacity is affected by both the bulk and surface characteristics of pristine materials, which is strongly influenced by precursor chemistry. The PITT results suggest that cation rearrangement during the charge/discharge has a significant impact on the lithium chemical diffusivity.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Shared Research Equipment Collaborative Research Center
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1024656
• Journal Information: Journal of the Electrochemical Society, Vol. 157, Issue 11; ISSN 0013-4651
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CAPACITY
CATIONS
CHEMISTRY
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRODES
ELECTRONS
FURNACES
LITHIUM
OXIDES
PRECURSOR
RESOLUTION
SCANNING ELECTRON MICROSCOPY
SPECTRA
SPECTROSCOPY
SYNTHESIS
TITRATION
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY