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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/451

Title: Ramsdellite-MnO2 for lithium batteries: The ramsdellite to spinel transformation
Authors: Thackeray, MM
Rossouw, MH
Gummow, RJ
Liles, DC
Pearce, K
De Kock, A
David, WIF
Hull, s
Keywords: Ramsdellite-MnO2
Manganese dioxide
Lithium batteries
Electrochemistry
Sciences
Issue Date: Jun-1993
Publisher: Pergamon Press Ltd
Citation: Thackeray, MM, et al. 1993. Ramsdellite-MnO2 for lithium batteries: The ramsdellite to spinel transformation. Electrochimica Acta, vol 38(9), pp 1259-1267
Abstract: A pure and highly crystalline form of ramsdellite-MnO2 has been synthesized by acid treatment of the spinels LiMn2O4 and Li2Mn4O9 at 95°C. Although the ramsdellite-MnO2 framework remains intact on lithiation at 70°C, the hexagonally-close-packed oxygen array buckles towards a cubic-close-packed structure to accommodate the inserted lithium ions. The reaction is reversible but the instability of the structure on cycling limits the utility of ramsdellite-MnO2 as a rechargeable electrode in lithium cells. The ramsdellite structure can be stabilized by reaction with LiOH or LiNO3 at 300-400°C; this reaction, which displaces manganese ions from the MnO2 framework into interstitial octahedral sites generates spinel-related domains that coexist with the lithiated ramsdellite phase. At 300°C, under vacuum, the lithiated ramsdellite phase Li0.5MnO2 transforms to the spinel LiMn2O4; at 300-400°C, in air, it oxidizes slowly and transforms to a defect spinel LiMn2O4+delta (0 < delta < = 0.5) via an intermediate compound. A mechanism for the ramsdellite-spinel transition is proposed.
Description: Copyright: 1993 Pergamon Press Ltd
URI: http://hdl.handle.net/10204/451
ISSN: 0013-4686
Appears in Collections:General science, engineering & technology

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