Studies of Mg-substituted Li{sub 4x4}Mg{sub x}Ti{sub 5}O{sub 12} spinel electrodes (0{le}x{le}1) for lithium batteries.
Magnesium-substituted Li{sub 4-x}Mg{sub x}Ti{sub 5}O{sub 12} spinel electrodes (0<x {<=}1) have been investigated as insertion electrodes for lithium batteries. The substitution of divalent Mg ions for monovalent Li ions in the structure necessitates that the difference in charge must be compensated by a reduction of an equivalent number of Ti cations from Ti{sup 4+} to Ti{sup 3+} . The substitution increases the conductivity of the [Ti{sub 5/3}Li{sub 1/3}]O{sub 4} spinel framework by many orders of magnitude, from {sigma} <10{sup -13} S cm{sup -1} for insulating Li{sub 4}Ti{sub 5}O{sub 12} (x = 0), in which all the titanium ions are tetravalent, to {sigma} = 10{sup -2} S cm{sup -1} for Li{sub 3}MgTi{sub 5}O{sub 12} (x = 1.0), in which the average titanium oxidation state is 3.8. The improved conductivity decreases the area specific impedance of Li/Li{sub 4-x}Mg{sub x}Ti{sub 5}O{sub 12} cells and increases the rate capability of electrodes for small x, typically x = 0.25. The rechargeable capacity of Li{sub 4-x}Mg{sub x}Ti{sub 5}O{sub 12} electrodes, particularly those with x close to 1 (130 mAh/g), is inferior to that of unsubstituted Li{sub 4}Ti{sub 5}O{sub 12} electrodes (x = 0, 150 mAh/g); the smaller capacity is attributed to the partial occupation of tetrahedral (8a) sites by Mg ions in the spinel structure.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); EE
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 942961
- Report Number(s):
- ANL/CMT/JA-36280; JESOAN; TRN: US201002%%465
- Journal Information:
- J. Electochem. Soc., Vol. 148, Issue 1 ; Jan. 2001; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- ENGLISH
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