Investigation of ramsdellite titanates as possible new negative electrode materials for Li batteries
Transition metal oxides with ramsdellite and spinel structures have been the subject of considerable investigation as candidate electrode materials for lithium-ion batteries. Good ionic conductivity has been reported for the ramsdellite Li{sub 2}Ti{sub 3}O{sub 7}, and the spinel Li{sub 4}Ti{sub 5}O{sub 12} has been shown to exhibit good electrochemical properties as a Li-anode material. The authors have recently demonstrated that ramsdellite series Li{sub 1+x}Ti{sub 2{minus}2x}O{sub 4} displays a complete range of solubility at high temperatures between compositions LiTi{sub 2}O{sub 4} and Li{sub 2}Ti{sub 3}O{sub 7} and that these phases can be preserved to room temperature by quenching. In this study they report on the electrochemical properties of members of this series of ramsdellite phases and the ramsdellite form of TiO{sub 2}. Comparison is made with the electrochemical properties of the spinel phase Li{sub 4}Ti{sub 5}O{sub 12}. In cyclic voltammetry, spinel Li{sub 4}Ti{sub 5}O{sub 12} showed a major, reversible peak at about 1.55 V vs. Li. The ramsdellite phases showed a similar reversible peak at just less than {minus}1.5 V; however, a number of additional reversible peaks were observed at up to 2.0 V. As the x value in Li{sub 1+x}Ti{sub 2{minus}2x}O{sub 4} increased, these extra peaks moved to smaller potentials, and they were observed to merge with the 1.5 V peak for Li{sub 2}Ti{sub 3}O{sub 7}. The presence of these extra peaks is thought to reflect the availability of additional sites in the ramsdellites. On charging and discharging, the potential was in the range from 1.5 to 2.5 V, although the behavior was not as flat as for the spinel. High capacities were observed, typically approaching 200 mAh/g. Initial cycling efficiencies were generally on the order of 80--90%, although no attempt has yet been made to optimize morphology. On cycling TiO{sub 2} ramsdellite, capacity generally faded from an initial value of 300 mAh g{sup {minus}1} to a stable capacity of 190 mAh g{sup {minus}1} by cycle ten.
- Research Organization:
- Univ. of St. Andrews, Fife (GB)
- OSTI ID:
- 20013018
- Journal Information:
- Journal of the Electrochemical Society, Vol. 146, Issue 12; Other Information: PBD: Dec 1999; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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