Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 505, Issue 1, Pages 367-373Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2010.04.253
Keywords
Lithium titanate; Combustion synthesis; Solid-state reaction; Titanium dioxide
Categories
Funding
- Outstanding Young Scholar Grant at Jiangsu Province [2008023]
- National Basic Research Program of China [2007CB209704]
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The formation mechanism of a spinel-type lithium titanate Li4Ti5O12 with TiO2 anatase as raw material, in both a conventional solid-state reaction (SSR) and a cellulose-assisted glycine-nitrate combustion (cellulose-GN) process are comparatively studied. XRD characterization demonstrates high-purity Li4Ti5O12 forms at 750 degrees C by the cellulose-GN synthesis, which occurs at a temperature at least 100 degrees C lower than that via SSR. The solid-phase reaction between TiO2 and lithium compounds to form Li-Ti-O spinel and the phase transition of TiO2 from anatase to inert rutile phase occur competitively during both synthesis processes. SEM results suggest that the solid precursor from the cellulose-GN process has a smaller particle size and a more homogenous mixing of the reactants than that in the SSR. Temperature-programmed oxidation experiments demonstrate that cellulose thermal pyrolysis creates a reducing atmosphere, which may facilitate the oxygen-ion diffusion. Both factors facilitate the formation of Li-Ti-O spinel, while the TiO2 anatase transforms to TiO2 rutile during the SSR, which has slow lithium-insertion kinetics. As a result, a high calcination temperature is necessary to obtain a phase-pure Li4Ti5O12. Charge-discharge and EIS tests demonstrate the Li4Ti5O12 obtained by the cellulose-GN process shows much better low-temperature electrochemical performance than that obtained by standard SSR. This improvement attributes to the reduced particle size due to the lower synthesis temperature. (C) 2010 Elsevier B.V. All rights reserved.
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