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.

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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.

From the in situ FTIR spectroscopy of the electrode/electrolyte solution interface at pH values of 1.2, 2.0, and 3.4, it can be confirmed that the adsorbate associated with the anomalous peaks in the cyclic voltammetry of Pt(111) in sulfate-and bisulfate-containing solutions is not the sulfate anion. The structure of the bisulfate-like adsorbate is tentatively postulated to be a sulfate ion/hydronium ion ion pair: SO 4 2-‚H3O + . Over the potentials in question, and only in solutions with appreciable HSO4 -concentration, can IR bands be found that are associated with the adsorbed species.