FTIR, IR, and XPS have been used to study the films formed on lithium in propylene carbonate solutions of LiClO4 , LiAsF6 , and LiSO3CF3 . Over a range of conditions, the main components detected in the initial surface films were lithium alkyl carbonates false(RCO3normalLi,R=normalalkylfalse) . Another alkyl carbonate solvent, diethyl carbonate, was found to react with lithium to form lithium ethyl carbonate, CH3CH2CO3normalLi . In addition to solvent reduction, XPS measurements gave indication of salt reduction reactions. LiClO4 , LiAsF6 , and LiSO3CF3 were reduced by lithium to form halide ions, which were detected on the lithium surface. Two possible mechanisms for the formation of alkyl carbonates are discussed. One is the nucleophilic reaction of propylene carbonate with basic species such as OH−, while the other involves one‐electron reduction of propylene carbonate by lithium metal, followed by free radical termination reactions. When high concentrations of water were present, lithium carbonate was formed by further reaction of the alkyl carbonates with water. On lithium surfaces without a mechanically stable surface film, such as those of lithium/mercury amalgams, the reduction reaction is believed to proceed by an overall two‐electron process, and the primary product is lithium carbonate.

No abstract

Surface films formed on lithium metal in dimethoxyethane (DME) and tetrahydrofuran (THF) solutions of LiClO4 , LiAsF6 , and LiSO3CF3 were analyzed using FTIR, SIMS, and XPS spectroscopies. The films formed in both solvents were found to contain lithium alkoxides. The main reaction products detected with FTIR were LiOCH3 in DME, and normalLiOfalse(CH2)3CH3 in THF. SIMS measurements are consistent with this finding. Reaction mechanisms are discussed. When the water concentration in these systems is 0.01M or greater, normalLiOH is formed on the lithium surface and appears to be a major component in the surface films. XPS measurements gave evidence for simultaneous salt reduction on the lithium surface in addition to the solvent reactions.

We describe synchroton based X-ray diffraction techniques and issues related to in situ studies of intercalation processes in battery electrodes. We then demonstrate the utility of this technique, through a study of two batches of LiMn2O4 cathode materials. The structural evolution of these spinel materials was monitored in situ during the initial charge of these electrodes in actual battery cells. Significant differences were observed in the two batches, particularly in the intercalation range of x = 0.45 to 0.20. The first-order structural transitions in this region indicated coexistence of two cubic phases in the batch 2 material, whereas the batch 1 material showed suppressed two-phase coexistence. Batch 2 cells also indicated structural evolution in the low-potential region below 3.0 V in contrast to the batch 1 material. Differences in structural evolution between batches of LiMn2O, could have important ramifications in their cycle life and stability characteristics. 466 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.48.29.181 Downloaded on 2014-11-03 to IP 10 x-ray photon energy (keY) 100 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.48.29.181 Downloaded on 2014-11-03 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.48.29.181 Downloaded on 2014-11-03 to IP ABSTRACTChemical reactions taking place at elevated temperatures in a polymer-bonded lithiated carbon anode were studied by differential scanning calorimetry. The influences of parameters such as degree of intercalation, number of cycles, specific surface area, and chemical nature of the binder were elucidated. It was clearly established that the first reaction taking place at ca. 120-140 °C was the transformation of the passivation layer products into lithium carbonate, and that lithiated carbon reacted with the molten binder via dehydrofluorination only at T> 300 °C. Both reactions strongly depend on the specific surface area of the electrodes and the degree of lithiation.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.48.29.181 Downloaded on 2014-11-03 to IP

The Electrochemistry of Noble Metal Electrodes in Aprotic Organic Solvents Containing Lithium Salts-(electrochemical behavior of polycrystalline Au and Ag electrodes in propylene carbonate, DME, and THF solutions containing LiClO4, LiAsF6, LiSO3CF3, or Bu4NClO4). -(AURBACH, D.; DAROUX, M.; FAGUY, P.; YEAGER, E.; J. Electroanal.