The elemental impurities in four different, commercially-available lithium samples have been determined. Cells consisting of these lithium samples as anodes and pressed acetylene black as cathodes were discharged at 20 C and at 70 C at a rate of 50 mA/sq cm. The passivating films remaining on the lithium surface after discharge were examined using electron microscopy and their elemental compositions determined using the surface sensitive technique of X-ray photoelectron spectroscopy. Performance characteristics (voltage and capacity) of test cells consisting, in part, of the different lithium samples are discussed in terms of impurity concentrations determined by secondary ion mass spectrometry and atomic absorption spectroscopy. The permeability and electronic conductivity of the LiCl passivating films are adduced as two possible reasons for the variations in capacity and on-load voltage of the different lithium samples. 25 references.