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|Title:||Metal oxyfluorides TiOF2 and NbO2F as anodes for Li-ion batteries||Authors:||Reddy, M.V.
Subba Rao, G.V.
|Issue Date:||22-Nov-2006||Citation:||Reddy, M.V., Madhavi, S., Subba Rao, G.V., Chowdari, B.V.R. (2006-11-22). Metal oxyfluorides TiOF2 and NbO2F as anodes for Li-ion batteries. Journal of Power Sources 162 (2 SPEC. ISS.) : 1312-1321. ScholarBank@NUS Repository. https://doi.org/10.1016/j.jpowsour.2006.08.020||Abstract:||Lithium insertion and extraction in to/from the oxyfluorides TiOF2 and NbO2F is investigated by galvanostatic cycling, cyclic voltammetry and impedance spectroscopy in cells using Li-metal as a counter electrode at ambient temperature. The host compounds are prepared by low-temperature reaction and characterized by powder X-ray diffraction (XRD), Rietveld refinement and Brunauer, Emmett and Teller (BET) surface area. Crystal structure destruction occurs during the first-discharge reaction with Li at voltages below 0.8-0.9 V for LixTiOF2 as shown by ex situ XRD and at ≤1.4 V for LixNbO2F to form amorphous composites, 'LixTi/NbOy-LiF'. Galvanostatic discharge-charge cycling of 'LixTiOy' in the range 0.005-3.0 V at a current density of 65 mA g-1 gives a capacity of 400 (±5) mAh g-1 during 5-100 cycles with no noticeable capacity fading. This value corresponds to 1.52 mol of recycleable Li/Ti. The coulombic efficiency (η) is >98%. Results on 'LixNbOy' show good reversibility of the electrode and a η >98% is achieved only after 10 cycles (range 0.005-3.0 V and at 30 mA g-1) and a capacity of 180 (±5) mAh g-1 (0.97 mol of Li/Nb) was stable up to 40 cycles. In both 'LixTiOy' and 'LixNbOy', the average discharge and charge voltages are 1.2-1.4 and 1.7-1.8 V, respectively. The impedance spectral data measured during the first cycle and after selected numbers of cycles are fitted to an equivalent circuit and the roles played by the relevant parameters as a function of cycle number are discussed. © 2006 Elsevier B.V. All rights reserved.||Source Title:||Journal of Power Sources||URI:||http://scholarbank.nus.edu.sg/handle/10635/97178||ISSN:||03787753||DOI:||10.1016/j.jpowsour.2006.08.020|
|Appears in Collections:||Staff Publications|
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