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Nanometric mixed iron-titanium oxides were prepared by mechanical milling with a view to determining their ability to act as anodic materials in lithium cells. At a TiO 2 /Fe 2 O 3 mole ratio of 0.4, a solid-state reaction occurs that leads to the formation of Fe 5 TiO 8 , which possesses a spinel-like structure; at lower ratios, however, the structure retains the hematite framework. Li/g-Fe 2 O 3 cells exhibit poor electrochemical reversibility; by contrast, Ti-containing electrodes possess improved cycling properties. Changes in the electrodes upon cycling were examined by X-ray photoelectron spectroscopy ͑XPS͒. XPS data confirm the participation of electrolyte in the electrochemical reaction and the different type of electrochemical reversibility exhibited by samples. Both processes were influenced by the presence of titanium. Titanium dioxide, in the presence of iron oxides, seems to be inactive to the electrochemical process. Based on the step potential electrochemical spectroscopy ͑SPES͒ curves and photoelectron spectra obtained, the presence of Ti increases the reversibility of the redox reactions undergone by the electrolyte during discharge/charge processes. The increased active-material/electrolyte/inactive-material interaction which is reported here offers new perspectives for the use of well-known transition oxides as anode materials in Li-ion batteries.

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This study investigates the organic components of the solid electrolyte interphase (SEI) on the carbonaceous anodic electrode in LiCoO2 batteries using solid-state nuclear magnetic resonance (NMR) techniques. The electrolyte solvents, ethylene carbonate and diethyl carbonate, were enriched on the carbonyl carbon prior to cell assembly and conditioning in an attempt to trace the breakdown pathways of these components. A strong signal was seen, demonstrating that the carbonyl carbons of both electrolytes survive in some reasonable quantity as insoluble breakdown products on the rinsed electrode surface. This confirms that the fate of these carbons as consumed in the formation of CO2 is either not unique, or not as final product. Furthermore the central carbonyl carbon survives, not as an intact carbonyl species, but instead in the form of compounds in which the carbon-oxygen double bond has been disrupted. Formation of this class of species is likely initiated by a nucleophilic attack on the carbonyl carbon by one or more radical, alkoxy, carbanion or fluorine-containing ionic species formed from solvent and/or salt breakdown. These results suggest a new family of electrolyte breakdown products, predominantly consisting of binary, tertiary and/or quaternary ether-type compounds (i.e., orthocarbonates and orthoesters), as well as fluorine-containing alkoxy compounds.