The effect of various solvents, lithium salts and Lewis acids on the conductivity of crosslinked lithium carboxylates resulting from the modification of maleic anhydride copolymers with styrene has been studied. It was found that in the presence of BF3 and polar solvents such as dialkyl sulfoxides or propylene carbonate polyelectrolytes can be obtained in the form of dimensionally stable membranes of ambient temperature conductivity of ≈10−3–10−4 S·cm−1. IR studies demonstrate a strong interaction between BF3 and carboxylic anions leading to a greater mobility of Li+ cations. The passivation phenomena at the lithium–gel polyelectrolyte interface for selected systems were examined by means of the impedance spectroscopy. It was found that the passivation layers could be formed in these systems both on the electrode and the polymeric membranes. The passivation process is strongly inhibited in the systems containing BF3.