This paper examines the behaviour of lithium polymer electrolytes based on aromatic sulfonamide salts tailored to optimize negative charge delocalization through the aromatic ring and up to the nitro substituents located in the para and para/ortho positions of the nitrogen of the sulfonamide anion. For the first time, lithium salt dissociation has been connected to the Σ + value. Thanks to the tailoring of these anions and to this physico-chemical approach it has been possible to show that resonance electron-withdrawing effects, as opposed to inductive ones, are decisive in reaching high conductivities in aprotic polymer electrolytes. Moreover the dissociation enhancement that can be expected, using the Σ + value of NO2, from the introduction of an additional nitro group, is in good agreement with the conductivity enhancement.