The electrochemical properties of a solid polymer electrolyte prepared by chemical crosslinking of PEO 2000 and containing LiAsF6 or LiCF3SO3 were investigated for electrochemical window, lithium stability and lithium/ electrolyte interface stability. FTIR spectroscopy of the salt anion (AsF6- and CF3SO3-) was also used to determine the nature and the extent of ion pairing and ion aggregation in these crosslinked electrolytes. The lithium corrosion appears as a diffusion limited process as the coulombic efficiency of a lithium deposit decreases with the square root of the contact time of lithium with the crosslinked PEO. Impedance parameters are consistent with an increase of the passivating layer upon storage. Their values strongly differ with the salt anion.